In general, better.
Wireless is all about signal strength and antenna positioning. The WORST place you can have a wireless card is behind a bug chunk of metal and interference - Your PC.
Your best bet is to get a USB wireless card and a USB extention cable. You can then move the card around to the place that it gets the best signal and leave it there.
edit: Unless it's for a laptop. If so, the USB ones like a memory card get broken off too easily and you should use a PCMCIA card.
- G