I also use vari-flo for my rats they work great. You do need to check them every month or two and make sure they are flowing good because they can plug up. They are easy to take apart and clean if they do. You may loose some rats if you don't check them.
Right now I use vari flow but I think I might try the other ones next to see how they compare.
i was kinda wondering that myself. i have been using those dew drip valves which i havent had a problem with for rats at all, but you cant use them with mice