I'd look at where the computer sits, myself.
If it's stuffed into a computer desk cubby hole where the metal case helps to block the signal, I'd go with the pci w/remote antenna. Especially if you have any distance to cover like across the house.
If the receiver is nearby, go with the USB2 one. If you have USB on the front of your case and signal blocking is a problem, put it there. But it's possible to knock it off while walking by the computer....
I like the pci/remote antenna ones myself. You can always engineer helper devices like a parabolic reflector, or even change antenna's alltogether to help boost weak signals. It just gives you more options.
With a USB one, if it's weak, you gotta go shopping again.
*New Thought! If you use a USB A male to USB A female extension cord, you can set your adapter up higher too. Never thought of that before....