For me, it's 4 eVod's, 4 min-pro tanks and one pro-tank. I rotate/sample quite a bit, so it's nice to have a few going at once. Plus I can defer my cleaning for a time when I want, rather than when required. I like them all fairly well, but still trying to perfect the pro-tank. Had I to do it over again, I probably would have gotten more mini-pro's and less eVod's, but I do like the eVod's for their sturdiness and appearance.