Thank you everyone for replying.
I play Hassidic and Klezmer music which is normally played at high speed - 160bpm and up. My styles are extremely live, and in the course of a single song, I could change styles 3 or 4 times. For example, instead of having 1 style with 4 variations, I have 1 style with 20 variations and in order to get to those other variations, I change beats. That's why I need it to be extremely quick and agile.
The HD is deffinitely too slow; the usb flash drive is deffinitely better - I was just wondering if there was an even faster alternative. Unfortunately, my onboard flash drive is already full with other styles.
I guess I'll use the USB.
Thank you all for your responses.