Main thing is the tank, large size. The dripper we have has four holes so makes it really easy to do duals, that is literally all I like about the dripper. Preferably wanting decent air flow, got a sigelei 150 and at moment have a sense herakles tank on it which has pretty decent air flow on fully open, anything on par for air flow is good for me. Not really fussed on cost at moment, obviously the cheaper the better but don't mind paying more if the quality is right, I'd rather pay higher once than lower twice if that makes sense