I had a buffalo airstation wireless pc-card ($25 from Target once upon a time for the mac-compatible model) and the aironet 350 ($120 originally) at the same time. They both performed within a couple of points of each other, no measurable advantage to either. The buffalo card could accomodate my Lucent Range Extender Antenna, but it seemed not to make a difference at the moderate distances I have. It might make a difference at long distance. The Range Extender also plugged into my Buffalo basestation, but again, PCworld mag rated it's internal antennas tops at reception, so there was no statistical difference in reception at moderate distances.
I agree that finding out which chipset is inside any model at any particular time is difficult, which is why having a good return policy is important. If you can find the card locally at a big-box store, that's even better.