On the surface, deciding is much like deciding about fellowship, go through your rotations, talk to your co-fellows and attendings and see what you are interested in. The super-fellowships don't have a match, so you'll need to work with your mentors to find places, although most stay at their home institution for advanced training. The pay is the same, but a little more (you're still a fellow, not an attending). Just like residencies and fellowships, some require additional years for research and some don't. Call will vary as much as it does with residencies and fellowships.
