I would get a USB one. The major benefit is that you can move them around if they have or you buy a USB extension for them.
Newegg.com - Rosewill RNX-N180UBE Wireless Adapter IEEE 802.11b/g/n USB 2.0 1T2R / 5 dBi External Antenna / Up to 300Mbps Wireless Download Data Rates 64/128-bit WEP (Hex & ASCII), WPA/WPA2, WPA(TKIP with IEEE
I bought this one for my brother to replace a PCI card he had. It has a decent length of cable to move it around and it has a larger, higher powered antenna than most others. He connects to a router about 120 yards away and gets a "good" (4 out of 5 bar) signal. His older PCI card barely managed a connection at that same distance.
