11.1v to 12v vs 14.8v to 12v
Be aware that a nominal 11.1v battery is 3 LiPo cells, or 3S, which could range from as low as 8.1v to as high as 12.6v. Similary the 4S battery could cover 10.8v to 16.8v. However, you don't need to use all of the range, at the cost of capacity. A standard charger will always tend to give you the top of the voltage range, but you can curtail the use before it drops to the bottom of the range.

As the 3S would need both buck and boost to cover your 12v requirement, it's probably easier to use buck only from your 4S battery, and not use the bottom part of the range. 

Ideally you'd use a 2S or a 5S, and then the whole discharge voltage range will be covered with a single boost or buck converter respectively.