I like biowheels on smaller tanks. Even planted ones I like them simply because of how easy it is to swap bacterial colonies around etc. You can easily use Flourish Excel for a source of carbon for plants on smaller tanks. But, on bigger tanks, it's simply not as cost effective as pressurized CO2 and if I am spending money on pressurized CO2, I'll be using a canister, not a biowheel. Just like anything else, everyone has their preferences, solutions and reasons.