Personally, I really like having bunks, really hate having to make / take down the sofa and dinette every night / morning and love being able to use the front of the mh while the kids are asleep so I'd be very hesitant to get a non-bunkhouse mh but there are definitely some compromises and there are a lot of different floor plans (you can get bunkhouses under 32' to over 42') so you can't really make a blanket statement about closet space and seating arrangement.
As far as the booster, with a lap belt only, it doesn't make any difference but our oldest (8) still uses his because he likes it (usually at the dinette with lap belt). Our youngest (3) is still in his child seat in the corner of the J-sofa. If we're in motion, the belts are on (in the very rare occasion, we might let the oldest go to the bathroom while we're on the road but that's quite rare and really only if there's no suitable place to stop).