Mac OS X has gone through several revisions and is being continually improved. This area discusses pros and cons of various versions of Mac OS X.
Version 10.13 macOS High Sierra
High Sierra features a new high-performance file system, APFS, which is initially only automatically used for SSDs. The Metal graphics system will improve game performance when it is used by future developers. And some improvements to the built-in apps, especially Safari and Photos are also useful.
Version 10.12 macOS Sierra
This system introduces new features which concentrate on standardising the functions of the Mac, iPhone, and iPad. The different systems have more functionality and there is increased interoperability between them.
Version 10.11 El Capitan
This is mainly a performance upgrade to the previous OS version, Yosemite. Apple have improved application launch times, made scrolling faster, and added other enhancements, partly through the use of a new hardware acceleration model called "Metal". There are some new features too. Safari now has pinned tabs which allows important pages to be left open, and individual pages can have the sound muted with one click. Spotlight now provides a wider range of results which includes news and weather, and it also suports some natural language searching. And a new window management system allows easily splitting the window of two apps on the screen.
Version 10.10 Yosemite
Yosemite is primarily concerned with improving integration with iPhones and iPads, especially through Apple's latest iteration of their cloud service, iCloud Drive, which does seem to work quite well (finally). There are also some improvements to built-in apps, but in the initial release some of these did have a few issues. As I write this the latest revision is 10.10.3 and that seems relatively stable. Since any machine which can run 10.9 can also run 10.10 and I don't know of any current programs which break between the two, I recommend taking the free upgrade to Yosemite in the app store, especially if you want better integration with an iPhone and/or iPad.
Version 10.9 Mavericks
Apple ran out of cool cats so now operating systems are being named after famous locations in California. Mavericks is a well-known surf beach. This system has some excellent efficiency features which make it run faster and with less resources (resulting in better performance and longer battery life on laptops) on most Macs. Initially there were some issues with Mail accessing GMail accounts but these were mostly fixed in 10.9.1.
Supported models are: an iMac, mid 2007 or newer; a MacBook, late 2008 aluminium, or early 2009 or newer; a MacBook Pro, mid to late 2007 or newer; an Xserve, early 2009; a MacBook Air, late 2008 or newer; a Mac Mini, early 2009 or newer; or a Mac Pro, early 2008 or newer. Other requirements are: 2GB of RAM (realistically 4 or 8), 8GB of available disk space, and OS X 10.6.8 or later (to install form the app store).
Version 10.8 Mountain Lion
Mountain Lion fixes most of the problems with Lion and I recommend most people to use it. It is a cheap update in the Apple app store.
Supported models are: an iMac, mid 2007 or newer; a MacBook, late 2008 aluminium, or early 2009 or newer; a MacBook Pro, mid to late 2007 or newer; an Xserve from early 2009; a MacBook Air, late 2008 or newer; a Mac Mini, early 2009 or newer; or a Mac Pro, early 2008 or newer. Requirements are: 2GB of memory (4GB better and 8GB recommended). 8GB of available disk space. OS X 10.6.8 or later (to install from the app store).
Version 10.7 Lion
Lion is not Apple's finest operating system. After installing the available updates it is fairly reliable but functionally it is a bit lacking. plus there are the numerous examples of the Skeuomorphic design which both look a bit ugly and reduce functionality. Lion also loses the ability to run PowerPC programs. I don;t recommend this system in most cases: upgrade to 10.8 or 10.9 instead. Of course, check compatibility of your hardware and specialised programs first!
Version 10.7 Lion Preview
Pre-release versions of Mac OS X 10.7 have been released to developers and some details are appearing on certain web sites. The major theme with Lion seems to be integrating features from the iPhone and iPad system (iOS) into Mac OS X. Since iOS is based on Mac OS X this sort of completes the cycle.
Version 10.6 Snow Leopard
Mac OS X 10.6 was released in August 2009. The major aim was to make the system more efficient and stable rather than to introduce a lot of new features. The major improvement for some users is significantly better support for Microsoft Exchange email and calendar servers which are (unfortunately!) common in large corporations.
One way this system was made more efficient was to drop support for some older technologies! Most importantly Snow Leopard only runs on Intel-based Macs so users of older PowerPC machines cannot use it at all. By default Rosetta (the system software which allows PowerPC programs to run on Intel processor based computers) isn't installed (do you get the impression that Apple really wants people to concentrate on Intel programs). Also support for Classic programs is gone completely. And not all printer drivers are installed unless the user requests them.
The memory requirements are similar to 10.5. It's possible to run using 1GB but 2GB is a more realistic minimum and 4GB (which is the minimum installed for all new Macs during most of the time 10.6 was bundled) is a lot better.
Version 10.5 Leopard
Leopard was released in October 2007 and at the time I wrote this (June 2008) has already had 3 updates (the current version is 10.5.3). The initial release had a few issues but these seem to have been corrected by the updates. Its important to make sure the updates are applied to all Leopard systems. Very few programs were "broken" during the transition from Tiger to Leopard but some issues were corrected with updates which should be applied.
The Classic environment was dropped form leopard, even on PowerPC based Macs, so that option is no longer available. There are native Mac OS X alternatives for almost all programs but unfortunately these might be paid updates.
Apple recommend at least a PowerPC G4 867 MHz processor, any G5 processor, or any Intel Core or Core 2 processor to run Leopard. At least 512M of RAM is required but this is really inadequate to do anything every useful and I would suggest 2G is more realistic although 1G is adequate if not too many programs need to be used simultaneously.
Version 10.4 Tiger
Tiger is very stable - I don't even know what its kernel panic screen looks like! The new bundled programs are also very good, and I can't remember a single case of Safari, Mail, Preview, iPhoto crashing. Why can't Microsoft do this? Automator, Spotlight, and Dashboard all seem to be very successful, based on how many components have been written to make use of them. The only problem is that Tiger needs a bit more memory (512MB is a realistic amount) and a few programs have some compatibility issues (retrospect backup has been the main problem for me).
Version 10.4 Tiger Pre-Release
Tiger is looking really good. Apple have reached the point where the general look and feel of the system is finalised and they can now concentrate on new functionality. All aspects of the new system are improving: core OS (a new kernel), systems services (such as Spotlight and Automator), and bundled applications (Mail, Preview, Safari, etc) are all solid and flexible.
Version 10.3 Panther
It just keeps getting better! Mac OS X 10.3 has more functionality than its predecessor, but its faster and just as stable. There's new user interface tweaks, like Exposé. There's improved core functionality like better printing and the addition of built-in faxing. The bundled applications are also better: Mail, Safari, and Preview are all considerably better than earlier versions. You might have to pay for it but I think the upgrade is worth it.
There's also lots of new functions like: Filevault (encrypts all of the user's data automatically), built-in fax sending and receiving, fast user switching (multiple users' workspaces can be active simultaneously), and new font management with Font Book.
Version 10.2 Jaguar
The release version of 10.2 removes the final little bugs in the preview version and maintains the improved performance. Although you have to pay for it, this is a worthwhile update to Mac OS X - everything just seems to run more smoothly.
Version 10.2 Jaguar Developer
The developer preview of Mac OS X 10.2 shows great potential in performance and flexibility but there is still some work to do to improve reliability (as would be expected for an early release like this). The biggest speed improvement is in application launch times which are consistently about half the current release version. Other parts of the system all feel faster although not to the same extent. My machines have older video cards so I don't expect huge improvements in that area.
The system has been made more flexible everywhere, including the bundled applications. The new version of Mail looks particularly good - most of the deficiencies in the previous version are gone. More bundled applications are included, for example the new iChat which I haven't yet evaluated.
This is an incredibly stable OS. On the rare occasions something goes wrong a force quit or the terminal can always be used to recover. Except when doing really silly things I never need to restart this system.
Performance is getting better but its a bit sluggish in places. The Finder isn't as configurable as it should be - for example, the text size can't be changed - and it also isn't as well threaded as it should be - some tasks stop others working temporarily. The Finder is missing some features it had in Mac OS 9 - for example pop-up windows, spring-loaded folders and color labels for icons.
Some of the applications are lacking features they perhaps should have - for example, Mail needs better filters and more flexible server handling.
This is still an excellent system - I would never go back to using Mac OS 9. It runs well on all G4 and G3 systems over 400 MHz. At least 128MB of RAM is needed and preferably more.
The first major revision of the system improves one of the more annoying performance issues - application launch times and brings better compatibility with peripherals as well as adding some useful new features.
The first release version of Mac OS X demonstrates the legendary stability and power of Unix with a wonderful Apple user interface. The performance isn't so good in many places - especially application launch times - but we expect this will be improved with time.
Preview Release 4
For a preview this is an incredibly stable OS! Unfortunately it is still a bit slow in some functions - some programs take too long to launch - and it feels a little bit incomplete in places as well (I have to keep reminding myself this is a preview).