Well if we are comparing apples to apples, with all other facts the same, such as:
Same car tested on both with chip installed
Same powerbase with no other change then switching digital to analog side.
No app used for either.
If so, your results would indicate that the digital side of the car/powerbase combo is using more power, thus car is slower when digital racing.
(There is no way to separate the powerbase from the car when testing apple to apple, so unknown is if chip itself uses less power itself, when running analog and the behavior of each revision of chips or if it is result of the powerbase alone or a combination of both)
If car is equal on both, install changers to see if that makes the difference.
Your results will be interesting here.
A 2nd power pack always helps, but it may or may not change this situation.
In the end , you are just playing with toys.