ewww @ 4wp. sorry i just have bad experiences with them.
anyways... KM2's are bad a** but it will tend to "skip" on curvy roads. DD is ok as long as ur not pulling hairpin turns. Its one of the lightest mt's available too, however with mt's..expect a drop in gas mileage.
15's are limited to 35's (there are bigger sizes but very limited to manufacturers) Best bang for the buck...great offroad look, cheap tires, cheap wheels, but you won't be able to upgrade to bigger calipers if the need arises.
16's are limited to tires. If your looking for a specific brand/size...do ur homework first before deciding on the 16's. They may or may not have it for the 16's.
17's falls in between mall crawler/ dual purpose rig. They have plenty of sizes available, but those expensive wheels maybe the case of the mall crawlers. i have 17's and although i have expensive wheels...like many of us, i do wheel with em. The price is the only con. my 33' wheel/tire combo...i couldve saved another grand if i went 35's/15's.
so in the end...its ur money, ur rig, and ur decision. Good luck. I'm just weighing the options for u...if i had to do it all over, with my type of jeep (dd/weekend warrior) i'd do the 15's.