I think it really boils down to what you are planning to use this OS for, if you are doing gaming, then the recommendation for more ram would definitely be good, and I would reccomend XP pro for that same reason. Also, if this is for home use, I would go XP pro. Windows 2000 Pro is limited compared to XP pro, which makes it a good client computer in the work place.
If you customize XP properly, it works pretty well. (Kill the System Restore, Error Reporting to Microsoft, Remote Assistance, kill a few services like Remote Registry, etc etc etc). I also like the XP theme service (provided you crack your uxtheme.dll file). One of the things I don't like about Win2k is, if I remember correctly, it names the windows folder Winnt or somethin like that, which can be problematic for installing programs that don't use the %SystemRoot% system variable (tho that's not many). blah blah blah.
Main thing is, Windows XP is pretty much 2k with some added features a lot of extra junk. Get rid of the junk and it works pretty well.
I know that System Restore can be a great tool for most people, but I've never needed to use it. Even if XP does get screwed up that bad, I've got 99% of all my data backed up on seperate harddrives and I'd rather have a fresh install rather than go back to settings that are old or screwed up. (That's just me.) Plus, I've made a little install script for XP, so reinstalling doesn't require as much of my attention. (Altho recustomizing the settings is annoying ) Again, it's just a personal preference.