Old news. General concession is Vista is slower than XP on the same hardware configuration. That starts with a default configuration. Of course, what is a default configuration? If you use OEM hardware, the default is quite a bit different from the OEM OS when purchased separately.
However, once you trim the fat from both operating systems, XP will be faster at most things. Stability wise, depends on the hardware, drivers, and the applications used. As an example, NVidia has had a hell of a time getting their Vista drivers stable.
There are functional differences between XP and Vista which contribute to more frustrations for many. As an example, Microsoft dropped the DirectSound API from Vista and DirectX 10. All sounds are now forced through the standard Windows sound API and Vista mixer. This added substantial overhead to all sounds being played in a game that depended on DirectSound, such as Aces High II. It contributes to poorer game performance on Vista.
The different configurations of hardware and software all lead to the wildly varying opinions on which is better. 'Better' being a very subjective term. XP can be screwed up by anyone and so can Vista. The people that feel Vista is a better choice normally come from XP installations that were borked up. People that claim XP crashed all the time had or have borked up installations. Unfortunately, it is easy to do.
The nature of Microsoft operating systems allows any application to screw up the operating system. The worst offenders of this are anti-virus programs. In Vista those programs finally got their own API so they should no longer have to replace system files in order to work. Those anti-virus programs probably contribute the most to the stability issues of any OS, but could have a higher impact on XP.
In our environment, XP is a far better solution. It is more stable and compatible. The Vista box we have, in its default configuration, is the most frustrating operating system I have ever dealt with. It starts with boot up times five times slower than XP, and goes downhill from there. Too many compatibility and stability issues. Even if the compatibility issues are solved, the general use of the OS is just frustrating and that is mostly due to UAC. Keeping in mind we have to run stock operating systems, we simply cannot turn it off as it is defaulted on by everyone.
My own experience has been less than stellar with Vista. In the last 5 years, or so, running Windows XP I have never had a lockup or blue screen or any other problem. It has been the most stable OS I have ever used from Microsoft. I worked with the Vista box fro about 6 months. During that time, I had to do a complete reinstall of the operating system three times due to corruption problems. Modern hardware and the same box ran XP just fine.
I have no doubt there are configurations of Vista running fine in the real world. I also have no doubt there are serious issues within the operating system simply because I had many serious problems and Microsoft says there are problems remaining they are working on.
