[lincpimp]

Personally, lipo seems to package better than a123. I have not really tested a123 cells, but have had great success with lipo. A 5000mah 5-6s lipo with the appropriate motor will produce great power and runtimes. A123 cells are 2300mah, so 2p is required for decent runtimes. But 2p setups get heavy.

I like lipo, and see no benifit from a123 for my use. Plus you have more choice with lipo for a charger, as not every lipo charger will do a123.