Of the cards currently sold, the performance is the same. The difference in the cards is because laptops come with different slots. So you buy based on what you have. PCMCIA/Cardbus or Expresslot. If your computer has no slots (or are going to use with a desktop PC) then you can buy the USB one. You can use the USB one even if your computer has a Cardbus or Express slot, if you wish.
I like my USB 881 as I can switch between different machines (notebook and desk top) easily, plus with a USB extension cable I can position the card differently (closer to window, etc.) for better reception. Downside is the external footprint of the card outside of the PC; you need to take extra care so as not to damage.