This tends to mostly be a personal preference since in general they work about the same. The USB advantage is it is very easy to make it remote from the computer with a 15ft USB extension cable. This allows optimum placement in the room without having to be close to the computer case. The PCI cards tend to have much better antenna and it tends to be easier to get devices with 3 antenna...ie 3x3 mimo support. You can get antenna extension for PCI but they are kinda expensive. If the PCI antenna have good view angle to the router you will likely get more signal, if you stuff it under the desk against the wall it won't work so good....then again neither will a USB dongle plugged directly in to the back of a computer.