Windows 2000 has been out since 1999, many more bugs and security issues have been fixed (or at least addressed) via periodic Service Pack releases than with Windows XP so there is definately an advantage to it and I can see why people would want to stick to that. - (I think 2000 is pretty good also)
That said though:
- Windows XP delivers 34 percent better performance when installed on a new PC than does Windows 2000.
- Average application access time is also 21 percent faster.
- It is also more configurable, giving you more control over your environment.
- Windows XP is also fully compatible with Windows NT 4, Windows Workstation, Windows Millennium, and Windows 98, and roughly 90 percent compatible with Windows 2000 applications, avoiding many of the compatibility issues that have plagued users of Windows.
Windows XP also offers:
- Built-in CD writer support.
- Remote Desktop Connection
- Internet Connection Firewall.
- Fast User Switching (useful for when multiple users are sharing one PC)
- Greater support for Windows 95/98 games and utilities.
Personal choice I guess but if you got the system and can afford it, I'd say go XP.