If the groups in the smaller cages aren't overcrowded, then it shouldn't make much of a difference, no. As long as the buck has scented all the territory, he'll feel comfortable getting cozy with the does. If they're a little cramped for space, though, in your smaller cages, stress could be affecting their willingness to copulate. Sex comes second to comfort for them, so if they're stressed out for any reason they won't give you litters as frequently. You could try giving them things to climb on and in, to try and increase the surface area in the cage where mice can be, and see if that increases your rates. Usually, though, in my experience so far, some bucks are just more eager breeders than others.