110W T5 vs 150W HPS?

[stinkyattic]

IF you have a HPS, definitely use it in flower. On very hot days, just use the T5 if your exhaust is inadequate, or add exhaust.
T5s are perfectly suited to vegging, so keep using it for that stage. Then you can add the HPS later.

If you have at least 3x3 feet of space, you might want to look into a HPS400. Sounds like you are already thinking about graduating to the big guns...