Need 5th Wheel Advice - Which Cab & Box on GM HD2500

I'm shopping trucks as well, crew cab only. Grandkids keep growing, two shelties and it's nice for the rare time we have adults with us. For the box, I'm a year from retirement. I use the truck we have now for commuting as well as towing, it's a short bed and I use a auto slide hitch. I'm looking for a long bed as soon commuting isn't a factor. If the right thing came along in a short bed I'm not opposed to it, but the long bed does give some more options when hauling stuff.