For no more difference in the cost between a 2500 and a 3500 SRW, I'd opt for the 3500 SRW truck....then no worries...IF loaded to 15,000, pin weight could hit 3,000#...at 14,000, could hit 2800#...I'd rather err to the side of safety than "just enough to get by with"....
I don't see how anyone can "guess" how much someone will load to...it's amazing how much one can load their RV too and may never really notice it unless they weigh before and after, or purchase another RV and empty contents from the old one into the new one...It might surprise some....I would want a truck that WILL cover the trucks GVW and the "possible" pin weight that it could possibly end up to being, instead of just "guess-timates"..