Sorry, but rats are not "better" than mice. Gram for gram, they are the same. It doesn't matter anyway since there hasn't been a study done on the nutritional requirements of Ball Pythons

I also have a few 2000g+ girls who beg to differ, they lub their meece! I had one rescue female gain over 1500g(she was 780 when I got her) from May 06 to December 06 on 3-4 medium adult mice a week(skipping a week here and there too). If that's not good gain, I don't know what is