If I was going to update from XP, I would skip Vista entirely. My only experience with Windows 7 has been in a business environment and our computers take a beating, so my opinion is probably not going to be very kind either. From everything I have heard about Windows 8, the interface was designed as a replacement for Windows CE/Windows Mobile.
If I were forced to update, I would go with a high-spec version of 7, probably Professional or Enterprise.