I feel they both have the potential to do damage, but if you are dealing with a rat, that is 2 or 3 times the size of a mouse, it would have the ability to inflict more damage per bite.
I find almost any rodent will fight back, but i've never seen one attack a snake(it may happen I just have never seen it), the problem is after the snake starts to constrict. If the rodent has an opertunity to bite the snake, it will bite to try to escape.
I don't know how hard it is to stun them, the two snake that don't eat frozed get live.
how many snakes do you have??
I breed my own rats, and they rarely bite me. Maybe because they are periodically handled during tank cleaning until they are large enough to feed off.
To the contrary mice have biten me regularly if given the chance.
I found when I had one colony I either had too many rats at one time or none at all when I needed them.
Think about it this way, you have two females, (I don't know why but my females in the same colony seen to aways birth at most 7-10 apart) so they birth about 12 pinks each, then it takes about 4 weeks to get them in the 50 gram range, so you feed 1.
Next week they are 55-60 grams, feed 1.
Next week they are 60-65 grams feed 1.
Next week they are 70-80 grams, feed 1.
Now the next week they might be too big for a small snake, and you have wait for another litter to birth.
The solution is to get your snake on frozen so you can freeze them at a good size for your snake to eat.
I keep 1.2 or 1.3 in a 10 gal and it is fine, but since it's small you have to clean the tank more often.
Good luck,
TomChambers