Either way, I don't see a poll on either one. (Safari on OSX 10.10.5) Should I just say what I prefer? If so then it's the bare chip ATTiny 85 in the PDIP package. It's pretty universal, easy to program, and really a lot of microprocessor considering its size!
If it's got to be an Arduino board, then the Micro. I have taken advantage of the extra 500K of RAM a couple times, plus it's really small considering all the stuff it can do.