My experience has been exactly the opposite -- PCI wireless cards have always been more troublesome than USB adapters for me, which was counterintuitive to how I thought it would be. After starting off broadband access with a USB adapter, I struggled with two or three cards from different companies, until I went back to USB for good, and haven't had a problem since.
In addition to thinking a card would work better, I also wanted WPA2 support -- the adapter AT&T provided only did WEP, which was also why I tried switching to a card initially.
I had one, a D-Link, that would eat the whole PCI bus every few seconds and max out latency (you could see this with the DPC tool), to the point that audio and video would stutter. I had trouble getting drivers to work correctly and consistently with the others, if I remember correctly.
Anecdotal, and everyone else's experience will probably be different, but that's how it turned out for me.
Last edited by stahlhart; 10-09-2011 at 07:46 PM.