I was in the same situation (between a Barton 2500 and P4 2.6C) and after reading countless benchmarks, reviews, and things people have said about them (and a lot from someone who owns both systems), I decided to go P4. Now I have used AMD for a while, actually here is my system history lol:
1997 - IBM Pentium 166
1999 - Gateway Pentium3 500 (mobo died so I rebuilt it with new mobo/case)
1999 - AMD K6-2 500 custom built (finally switched from the "dark side" lol!)
2001 - AMD Athlon T-Bird 1333MHz
2003 - AMD Athlon K7 SlotA 850 given to me (2 weeks ago)
future 2003 - P4 2.6 baby!
So as you can see I really am no Intel fanboy, but I just think that Intel has them beat! And its only costing me $70 more ($40 if you buy a aftermarket HSF for the barton to O/C - the P4 can use the stock retail one), so I really can't buy another barton and go out to lunch with $40...