The size of the boobs in a fight has nothing to do with fighting ability. I would go with the gal who is slimmer and in the best physical shape and agility.
I'm a man. I fought heavier opponents.
Struggling standing in the distance and shorting have better chances due to the higher speed. Of course, if fat man is more muscular, he has stronger punches and holds.
But in this question, we have two equally muscular girl. One is thicker and has bigger boobs.
I know that there is such a harder opponent throw off the fight on the ground. However, using the techniques associated with pain I'm projecting that he himself is falling, and I'm at the top.
The same applies to women. Pulling her hair, punching, digging fingers into eyes, choking, you can control your opponent. Even if she is greater. Fat girls play sports less, or not at all. They lack self-confidence too, because carry inferiority complexes ... even from school.