I love Premium Aquatics. I have always had good experiences with them except one time. They did not have what I ordered in stock, and they did not tell me until the day after they were supposed to be shipped, but it worked out. The difference in the bulbs is the color, wavelength, and K. Inorder to best get an idea of what you are getting into, you should probably look through some old threads with the bulbs being used, and the person tells you what they are using. I use MH and VHO now, although I think the T5s are great. I just like the shimmer from the MH and the intensity of the VHO is amazing (don't have alot of space in my hood). +1 on using good bulbs, like ATI, KZ and Geissman. I loved the KZ fiji purple. That bulb brought out the pinks and reds. Unfortunately, I don't have a good number of actinics to whites for T5s to suggest. I think I would prefer 2 whites to 4 actinics, but that is me. GL