This advantage that AMD has is most likely due to the Athlon's superior floating point performance. The advantage may not exist anymore (for the time being) due to the P4's soaring clock speeds - it doesn't matter so much if your cpu is inefficient if it has gobs of cpu cycles at its disposal. Another thing to look for is if these apps (or plugins) have SSE2 optimizations. If they do, then the P4 will probably smack the Athlon around.
For me, the primary concern here is not which cpu is faster, because they're both very similar in speed. What matters is system stability, and that's where I believe the P4 has an edge. VIA chipsets are somewhat notorious for instability problems, but stable AMD solutions are out there, you just need to do some research.