The minis require you to have a serial adapter of some sort to load sketches to it. Once loaded you don't need the serial adapter connected anymore but I found this to be a pain to get working first time every time. The USB nanos work first time, much less hassle.
I have 4 in use and I think I bought 5 nanos and 5 pro minis a while back.
EDITED: 4 Jan 2015 12:27 by ANT_THOMAS