If you are referring to controllers that ONLY have USB outs, you should beware... most of them, the fancy processing is done by the laptop AFTER it gets the basic USB key and knob/slider information.

Add to that that any information running down the USB cable has to share the data steam with every OTHER USB device on the chain, compared to MIDI being dedicated to JUST the musical data.

If I were you, I'd stick to controllers that have plain old fashioned MIDI. MIDI over USB is still in it's infancy, things like sys-ex and timing critical clock signals are still iffy (if a computer doesn't translate them.

Have you already GOT the controller you are going to use, or are you shopping right now?