The jump from 98 to XP was not nearly as bad as XP to Vista in terms of performance and RAM requirements.
The jump from 98 to XP also brought along many fixes to the overall architecture of 98.
Vista brings diddly-squat to the party except a ton of bloat, more restrictive DRM, more intrusive remote management, more restricted admin rights, and many other useless things which are there to help Microsoft and OEM's, not the user.