Third person perspective is easy-ish, in its way. You can see the world you created, your story world, as God might see us. You can zoom in far enough to see the ticking of thoughts in a single character's head, but you can pan out to show the whole of creation if you like. There's a great freedom in that sort of writing, and an intimacy, as well as a prestigious knowledge. In the third person, when done well, the reader doesn't see that the writer has control of the reins the whole time. The writer does, of course, but the reader trusts that he'll be led in the right direction.
First person is another animal entirely. Especially if you're working with multiple narrators as I am right now. You don't get inside a character's head so much as he gets into yours. I don't mean to be dramatic, but the closest way to describe writing in the first person is that it is like a sort of possession. The character isn't in your imagination, he's right in your face, moving your hands, your body, laying out for you the tracks on which the locomotive of your narrative will run. A good writer, an obediant writer who understands enough to get her own ego out of the way follows the path set out with grace, and fear too, because you don't know what's coming. But you follow because you must, because there is no choice otherwise. That's how it should work, anyway.