The XP series PR ratings are less accurate vs P4's at the high end. Most people agree that bartons and tbreds rated 2400+ and higher do not perform on the same level as P4's clocked at similar pr speeds.
2500+ is roughly equal to a 2.4 P4
2800+ = 2.53/2.66 P4
3000+ = 2.66/2.8 P4
3200+ = 2.8/3.0 P4
TBH it's not as simple as that, in most benches, one brand usually dominates the other ie a 2.4 P4 will beat a 3200+ in some benches while a 2500+ will beat a 3.0 in others.
Search sites like anand and toms for benchs, there are plenty, well maybe not toms they work in an intel office but there's plenty of other sites. What I'd go by if I was you is money. Price/performance-wise the two companies are lined up pretty evenly at the high end. Below the 2.4ghz P4 AMD's procs become a better value but above that point, xxx dollars of intel vs xxx dollars of amd buys similar performance. Use this method and you can disregard AMD's PR ratings.