There are several huge differences in the 2015+ F450's vs. F350's. Ford back in 2008 put the Dana110 rear end and 19.5 tires on 2008-2010, but then went back to the Dana80 on 17's through 2014. Why they did this I'll never know, because all they did at that point was to put in 4:30 gears and call it an F450.
The 2015+ F450's have a rear axle rated @14k just on it's own, and the 19.5 tires that can hold it. Dana80 on 17's is rated @10k per Dana's spec.
In addition, since they have larger rims, they also increased the size of the brakes all the way around. I had an F350 and traded up to the F450 and I can tell you the difference in loaded ride feel is tremendous.
That being said, I needed the F450 because of the weight of the camper I haul+trailer tongue weight of 1,000lbs. You won't need an F450 for just a 5'er or 'normal' camper. However, if someday you decide to ditch the 5'er and get a BIG camper, consider the extra few bucks now on an F450.
'15 F450, 30k Superhitch, 48" Supertruss, 19.5's, Torklift Fast Guns
'12 Eagle Cap 1160, 800watts solar, Tristar MPPT, Magnum Hybrid 3k Inverter
'15 Wells Cargo 24' Race Trailer, 600 watts Solar, TriStar MPPT, Xantrex 2kw inverter
'17 Can Am X3 XDS Turbo