I've used MH HPS and T5 and IMO there is very little difference for vegging - I use T5 for vegging. When it comes to flowering nothing beats the HPS. The T5 lights are 6500k - very blue and work well. I use 3000K T5 lights in summer for flowering and get about 20% less yield on average. It saves on the electric bill since I'm in a high desert climate where summer temps reach 90-105 regularly. I don't even use MH any more.