The advantage is that you're not going through the USB bus. The spec says 480Mbit but in real life it's much much lower. Does your rackmount server have quality USB2.0 (heh) or the cheapest 1.1 crap the manufacturer can find (likely)?

On the other hand I don't have hard numbers, just some bonnie tests on random flash sticks I had lying around. Check out the newer USB sticks that are "Readyboost Ready", such as Corsair. They might be quick enough.