Qantum boards need a fan blowing on top to get the ~2.7umol/J advertised efficacy, otherwise the fixture itself is a bit warm. which is important for re-cooping the extra cost of buying them. They will be cheaper over the lifetime one way or another and provide more photons per m^2. (the SF with Samsung LM301B diodes or LM301H - same exact thing, don't pay extra for an "H").