Personally I'd go for USB (firewire if you can), but then again, I'm on a macbook, so internal cards aren't really an option.
I use an MBox to run Protools, but it can also be used for Cubase, Logic, Sonar etc...
Lots of really useful features and good quality AD conversion too.
Protools ain't cheap though...
It also depends how many channels you want to record at once. MBoxes will only do 2 channels, so if you need more than that then I'd probably look elsewhere. Loads of people I know have made positive noises abut the focusrite saffire stuff - cheaper than protools too.
HTH
Paul.