This is a very, very subjective question.
If you have a small grow space, small budget, and only a few plants, then CFLs are by far the most economical. They don't get hot (easy to eliminate heat from grow space), they are relatively cheap (for the amount of light you need), and they are very versatile (can be placed in some of the most odd positions and as close to the plant you want).
Comparing CFLs to MH/HPS lights isn't really a fair argument. Bottom line, if you are just growing for personal use and need a compact but useable light source, CFLs are for you, the end. If you have 100 plants and multiple grow rooms and you're in a situation where you can freely and legally grow marijuana, then sure, you'd be better off investing in the more expensive lighting. It's not that hard, really.