I am building a hexacopter and will be using PixHawk as the flight controller and a Raspberry Pi for gimbal control as well as image processing. Now I see that I can use a 4s or 6s battery for powering my set up and a BEC can be used to convert the 14.8V/22.2V down to 5V for the electronics. Additionally, the ESC will use BEC to provide the correct voltage to obtain the required rpm of the props.
Now, from my research on BECs I understand that most use a resistor to reduce the voltage, thereby wasting energy in the form of heat. Based on this understanding, I feel that the 4s is a better option, considering total capacity is constant, for longer duration flight as in case of 4s the voltage drop required is less and hence less energy wasted. Is my understanding correct?
Second, is a resistance type BEC capable of handling 6S battery?
Further I understand switching BECs do not waste energy, so if I get a switching BEC which battery is better 4S or 6S, all other parameters remaining same and constant?