32GB USB 2 Drive - Recommended for iMac running Mountain Lion

Hi

I want to keep a separate copy of Mountain Lion on a USB drive so I can either use at home or on a family member Mac.

I want a fast and reliable drive, have looked at Sandisk and Corsair so far. Only have USB 2 on my machine at the mo, but would consider either USB 2 or 3.

Any recommendations would be appreciated.

Thanks in advance.

Matt