I've been told by two different vets that live rats/rodents are better for your snake. The reason being that all the bacteria in the rodent is actually good for snakes, and by freezing them you kill all the good bacteria.

I really dot know if this is completely true but it sounds very reasonable to me. As humans we do the same thing with yogurt and other foods, so why wouldn't it do the same for other animals. And I have noticed ever since I starting raising my own rats and feeding all my snakes live they seem to beach healthier.