i don't have a full cab, but the half doors on my xt max don't make it feel tight. I'm 240# and drive without issues. the front is the same size as the single bench machine, for reference. been in some cab defenders and never thought it was tight inside.
it is a big machine if it gets tight and you need to turn around, that's for sure. i have had it in a couple of spots that were tough to turn around and ended up getting stuck in some ruts once while trying to turn it, it was a bit of a pain to get it out where a single would have been much easier to turn around and not get it stuck because i could have got away from the ruts. if your trails are tight for your hd8 now, they will be much smaller driving a big bus around, the extra length is noticeable when maneuvering, not so much just driving it forward though.
i also need the big machine for my kid, dog, wife and all the extra stuff. a limited is certainly the way to go with a cab, esp if you ride in different temps and weather often. if you can swing the cost, do it. it's easier to have stuff on from the factory than try to add it all after the fact unless you plan to do it yourself. doing installs yourself isn't usually a fun time either, that's why dealers charge so much to install.
we put anywhere from 50-120 miles a day on it when we ride. unfortunately my xt seats aren't that great, it is not nearly as comfortable as our x3 is, so we stop often to get out to stretch I put zbros on it, that helped with the ride but the seats just get to be uncomfortable after sitting in them for a while.
steve