As far as HPS go what does your electric bill look like. I have a buddy that grows (i dont ask him all these questions cuz the less people who know what I want to do the better) and he grows with MH and I think HPS and he spends like 2G's a month on electricity
Well think about it.
If you have 6x 26w 100w equiv CFLs thats 156w and ~10200 lumens
If you have 4x 42w 150w equiv CFLs thats 168w and ~10800 lumens
If you have 1x 150w HPS light thats 150w and ~16000 lumens AND a shitload of heat.
If you have 1x 250w HPS lights thats 250w and ~33000 lumens double the heat output.
If you have 1x 400w HPS lights thats 400w and ~50000 lumens plus even more heat.
I could see running up a 2k bill with like 2+ 1000w bulbs though, because of the cooling costs.
It all depends on how big your space is, you need to build a setup for YOUR grow space.
If you don't have room to give your plants 9" of buffer space between the HPS and the tips when they are at max height then obviously, you aren't going to want to go with HPS.
If you have a larger area, HPS is ideal because of the penetration and sheer lumen output. You will need some kind of ducting or cooling for a HPS light.
If you have a smaller area, CFL is ideal because they put out close to no heat and you can space them out all around the plant just a few inches away.
Using cfls in a huge grow space would be kind of silly. But throwing 6 cfls in a cabinet thats sealed would be a good idea, wheras, a HPS light in there probably wont make your plants very happy because of the heat.
If you can tell us what kind of grow space you are working with, it would be much easier to recommend a medium.