how is an hps cooler then cfls?...an hps gives off way more heat then those bulbs
Because CFl's are not heat free. They operate on a lower level of efficiency than a 150w hps does and in the world of electronics the watts that don't go to light go to heat by default. The heat is spread out more because there are more heat sources at a lower level with each cfl, but cram those cfl's in a sealed box for an hour and record the temp and then stick a remote ballasted 150w hps in the same space for an hour and record that.
Both will be close, but the hps will actually be lower. Those cfl's will all start to cook eachother with no ventilation and their operating temp will skyrocket.
Bottom line, either way you will need to vent and you will need fans and either way will create heat so it frankly doesn't matter which type of light you choose. I only suggest hps because for the money... Duh...
(I'm no genius but I do have an associates degree in electronics)