Every light has its pros and cons.
MH/HPS:
Most tested light is MH/HPS up to 600w with great yields. It's efficiency can be improved by vertical growing in a concentrical arrange. The problem with mh/hps is its cost (bulb/ballast/reflector/cooling system) and the low energy efficiency, meaning it loses too much energy by heat emision and it has to be too distant from the plant.
CFL:
It has been growing in popularity last few years, gaining acceptance from experts growers. It's highly energy efficient, it doesn't emit too much heat and it can be placed closer to the plant. Its best quality is the high resin output, with CFL you'll get frosty buds no matter the yield's size, the reason for this can be found on it's UV output. Bad thing with bigger cfl bulbs is that they lose efficiency, going with many 23w cfl bulbs would be better than one 100w bulb. Their color range is not so efficient either for our purposes, 2700K and 6500K being the most common, while the color t° should be at 3000K - 4500K - 5700K. Plus, CFL tend to be more efficient horizontally placed, and it's harder to do so.
LED:
The most infamous one, it actually has been proben to be excelent for our purposes, COB LEDS have the lead for now, with better results than smd and other techs, using one high output 100w COB 4500K can be enough for a "little" plant.
More info about Leds on the forum.