mouse vs. rat, pinky vs. hopper??

[Thrush]

Hi! Just wondering what the differences in nutritional value are between the varying ages of the prey items and also between rats and mice. I have noticed that some people prefer one over the other, but haven't yet heard why? (of course, besides the obvious size issue of 'whatever fits in the snake's mouth)

Thanks, still learning about my baby corn...

ps.. I'm feeding my 7 month old corn 2 pinkies a week, I'm worried it's not enough, though, since he's growing slowly, or should I be happy that he's not growing too fast?