I don't want to get into contradicting anyone, but your best bet is possibly with firewire.
There isn't much around with usb 3.0 support yet and whilst usb 2.0 is faster than FW 400 on paper, it doesn't handle data in such a economic way. Google usb 2.0 vs Firewire 400 to read up on it.
Also you'd be using your usb for all sorts of stuff (mice keyboard and more etc.) which would mean that your usb powered Audio interface wouldn't run as well having to deal with the extra loads. Where as you could get a TI Firewire port (400 or 800 only no mixing here!) and 'just' run your audio interface through this so that the drivers stay nice and uninterrupted. The idea with Audio based computer applications is that it remains as clean as possible.
Agreed about Apple, not worth the $$££ imo. Hackintosh = updating issues from what I've heard. Someone else made a good post here on the Props forums about it.
I've only heard bad things about PCI/PCIe connections but I might be wrong!
At the end of the day if you run your gear with a good i7 quad (not i5, don't listen to the overclocking gamers!)minimum of 16 gigs ram and a good quality motherboard (Asus Z77 range is the current best for Audio applications) and a noise free graphics card (Sapphire Radeon 7770 is 0dB and GDDR5 and doesn't cost £300) then you'll have no problems with just about any Audio Interface and it's drivers/software.
Disclaimer: This is all pure speculation based on what I know and use + what I've read up myself.