I don't hold a strong opinion about which option is best, since there isn't one. Like I said, my bike is my main transportation (weather permitting),...
For sure, A123 of lipo are lighter, can give more amps, and yeah, you can build them up in stages. Although, you want to match the cells when you put...
If you're not building a race bike, and are worried about burning your bike up, don't use RC lipo. Go with LiFePO4. CALB are good, GBS are also good....