Gram per gram of prey it's all the same obviously there is an advantage in feeding rats, it is obviously more convenient to feed 1 prey versus multiples which you will have to at some point.

So is an adult mouse better than rat pup? No if they weigh the same there is no difference the food intake will remain the same and while the nutritional value is different there is however no study on nutritional requirement of snakes.

I mainly have rat eaters but I also have 2 mice feeders and they are doing as good as everyone else.