Hell of a Problem, 2WD or 4WD?

[6 Door King]

I have found myself with the worst possible problem to solve. I have at my disposal a 2WD crew cab dually, and a 4WD version, both with 454, TH400 and 4:10s. The question I pose for you all to weigh in on is this, Which would be more reliable in general for towing? The 4x4 is carbed and 2WD is TBI, 4x4 has 205 t-case and gooseneck hitch, where as the 2WD has fifth wheel hitch. Another concern is the fact that the 2WD has had a c-notch installed and it is less than a stellar install, which has me scared to do too much with the fifth wheel. Really looking for experienced haulers to comment and advise, also those that have towed with lowered or c-notched trucks. Thanks guys