Just to clarify a bit here, chipsets of FW400 is rarely (I would say never, but just in case) a problem. And since most laptops are equipped with FW400 you shouldn't need to worry. FW800 however is a different story. There I strongly recommend the Texas Instruments chipset.
I would really disagree on this, just search for "Firewire problem audio interface" and you'll get hundreds of forum threads about that. Apparently there is a complex set of problems you can have with firewire, lousy FW chips like the dreaded Ricoh, and driver problems... I tried to get my Firebox to run on many different systems and I never succeeded. Theoretically Macbook pros should guarantee good compatibility with FW interfaces, but with most other manufacturers it's a matter of luck finding a laptop that will work (the only ones that might work fine are the ADK laptops).
USB on the other hand seems to have less compatibility problems.
You need to look at a minimum of 200 USD investment to get a good card
Second that. see it like that, it's better to spend 200 now, than to spend 100 now and then have to spend 200 more next year after months of frustration.