Thirding the "cannot have too much truck" sentiment.
A 3/4 ton is at its payload / rear axle weight limit with any decent sized camper from the start.
A one ton SRW is well loaded, at least with most slide out campers. And you can not really increase the rear axle weight rating without going to 19.5 wheels in many cases where the tires are already at the load limit.
Both trucks can be just fine for the right camper.
If you do not want to limit your choices, go for a duallie.
A crew cab has a lot of extra storage in the cab, where stuff is more easily accessible.
As for Diesel/Gas... That is an almost religious question for many. But a good Diesel will pull better, that is for sure. Lots of discussions can be found on the web over this issue.
