Whether your snake feeds on rats or mice it doesn't matter. Whatever works for you; that said as your snake gets older its going to be easier to feed one appropriately sized rat as opposed to feeding multiple mice. If you were going to continue feeding mice I would look for something more along the lines of one size above what you pointed out in the link or this sized rat.

http://www.rodentpro.com/catalog.asp...el=frozen_rats

3rd size down