There is very little difference in price between a 3/4 & 1-ton truck, so in that regard buy whichever is the right platform for your needs. If indeed you are looking for a camper in the 2800 pound range, you may find it will likely be at or over the payload capacity of a 3/4 ton, so I would strongly consider a 1-ton. When I bought my truck, I started to look at used, but was frustrated by so many being lifted, have had tuners installed or kind of beat up. That and the generally high resale value of diesel trucks and not a lot of time to look, led me to buy new. If you have time there are deals to be had so look around.
Regards, Bruce, Lin An, Kenji and Suki
2017 Eagle Cap 1165
2015 Ram Big Horn CC 3500 TD, DRW, AISIN Tranny and 3:73 Gearing