The Pentium's are currently well out pacing the AMD's in terms of front side bus (FSB) speed, cache, and perhaps even clock speed (GHz). By outpacing I mean nearly double too.. I think the latest P4's have something ridiculous like an 800mhz front side bus, also have a 533mhz version. I think AMD is topped out right now at 400mhz perhaps. FSB could be considered your "motherboards speed", which is important because your IDE, PCI, and every other bus will be some fraction of that speed, ie. higher the better. I tend put a lot of focus into the FSB speed as there's a serious "MHz myth" about what is really *faster* and what has the highest numbers.
Will you ever *need* all that extra bandwith? Probably not, but it might speed up
teidius tedious things like resampling, I couldn't say for certain...
While it might be out of your price range (not sure what your looking to spend) if you honestly do a lot of intensive work on your PC with large audio files you might want to look for a dual processor mobo or the new home version of the Athlon64. Those would fly through large audio tasks like you wouldn't believe... a friend has a dual processor box and it's night and day.
Guess it depends on usage and yer wallet. I run an AMD 1700+ so I ain't even up to date myself
I just am sure to record at 44.1 all the time