According to the herpers here on this forum, yes rats will make em grow bigger faster!

The reason behind this is that rats are more nutritious than mice. But it all depend on the size of the rats. Some here argued that feeding 2 adult mice is better (in nutritient sense) than a single young rat.

Ideally, your snake should be fed a meal that is the same or slightly bigger than the thinkest part of its girth(body).