Im a strong believer that there is nutritional differences among prey items
What I mean is.. if you feed a BP (in this case) mice from the day its born and keep it on mice its entire life, then get another BP and feed it rats for its whole life. I would bet money that the rat fed BP will be bigger
I learnt this with boas a long time ago. I realized that mouse fed RTB's are TINY compared to my RTB Powder at just about the same age. Why is that? Well because I have always fed her a nice big juicy healthy rat. I only had to feed mice on two occasions and I dont plan to ever do it again.
What else did I learn about prey size in relation to RTB's size? If a RTB is kept on rats its entire life it will (Remember.. there are exceptions!) stay smaller infact MUCH smaller than a boa that has been fed on rabbits.
My reasoning for saying that is because I have seen all the threads on various forums about the INSANE growth spurt a boa can go through when it is fed on rabbits. I once saw a thread where a female boa got switched over to rabbits and then a year or two later I saw an update and she had grown from 7 foot to 9 - 10 foot.
I have seen plenty of evidence to convince me that certain prey items are better nutritionally than others