I use the Foodsaver v2440 and have been happy with it. I like this model because I can choose where to place a seal by opening the lid and placing the bag as I want it, as opposed to one of the newer models where you just insert the end of the bag into a slot that seals it. This way I can make individual pockets for each mouse rather than just tossing all of them into one bag. I don't do this for an entire mouse order, just when I open up a bag (for example, a bag of 25 adult mice).
With the large bags I can make two or three pockets large enough to fit an adult mouse in each. This way at feeding time I can just cut open one pocket to get a mouse, rather than opening up a bag, removing a mouse, then resealing the bag.
I don't know if it's the same for all sealers, but for this one every time you seal a bag, that sealed end uses up about an inch to an inch and a half of bag. So if you plan on dumping a bunch of mice in one bag, you need to make a long bag since you'll be cutting off that sealed part of the bag then resealing it.