Finishing nail gun vs impact driver
Impact drivers are great tools if you ever want to drive screws; they are far easier to use for this than drills are. I think a finish nailer is a bit more of a niche item; you can use it to put up trim (baseboard, casing, that kind of thing), but you can't use it for anything structural as the nails aren't big enough. 

I've owned two Makita impact drivers and have been happy with them, though mine are from the pro line and I don't know about the quality of the combo kits.