Sorry, not sure if someone brought this up before but this:
http://www.google.com/url?sa=t&rct=j...V578uGl8MNH9Dw (PDF warning)

ARM vs Thumb vs Thumb2. Performance(speed)-wise ARM trumps (check page 4), size is for thumb 1 and 2. I would love to see iozone benchmarks of course, but thought this might give some background.