CFL vs. HPS

[psteve]

Is the difference significant?

Which is 'easier'?

Yes. The difference is quite significant, but many people grow happily using CFL's.

Once they are set up, there is no difference in how easy or difficult they are. The timer turns them on, the timer turns them off. The difference is in how much heat they generate, and therefore how much temperature control you will need.
How much your bill goes up depends on a lot of things, and probably can't be accurately answered here without a lot more info.