[starscream]

This is an interesting question but I would think that any time you add an extra cell to the mix you'd be applying additional resistance so a 1P setup, with the same C rating, would be more efficient. In the case of the 8Ah 20C's and the 10Ah 15C's, I would think that the 20C cells would perform and be happier in slightly higher current setups and the 15C cells would give you longer runtimes in higher voltage applications. So, like usual, it doesn't seem very clear cut. What vehicle are you running and at what voltage?