Intel and Atheros-based wireless cards seem to be well supported in Linux. Are you looking at replacing the internal card, or using a USB/PC Card adapter?
What driver are you using for your Broadcom card, the open-source ones or the Broadcom-provided ones? I had a Dell Latitude D531 with a Broadcom wireless card, and used the Broadcom-supplied drivers under OpenSUSE. The drivers worked fine, but it got annoying having to recompile and update the driver every kernel update. My current Latitude D830 has an Intel 4965 card, and it works great.
Casey