When we bought our 318SAB, we looked at an awful lot of 5ers. Some had the front living room and at first blush, we really like the design and the rear bedroom was huge (well it looked that way with the tall ceiling).
Then we got to thinking about how we use the rig. We spend most of our "inside time" in the living room and kitchen. We aren't getting any younger and the thought of "up the stairs" "down the stairs" and then repeat, ad nauseum, every time that we wanted a munchie or a drink, etc. while in the living room turned it into a not so good design.
Then we got to thinking about the view. If there is a view, it most likely will be out the back. Not much to look at when you are asleep, and that's all we use the bedroom for; sleep (well a few other things, but, we keep the blinds closed for those:o) No need for all that "space", we go in once and go to bed. Get out of bed and come out; 2 times in and out and that's about it. All that space isn't apparent with our eyes closed.
Didn't like the bathrooms with a hall down the middle, the 318SAB has a separate bathroom, a huge rear living area with a computer "office", and a big enough dining room that we took out the dining room table and chairs and I put in one of the DW's looms. She can sit and weave and watch television; an arrangement that wouldn't be possible in a front living area rig.
They have their purposes and they fit a need; just not ours and I'm glad we kept looking and didn't go with our first "gee whiz" moment.
Going from a MH to a 5er will be big change; the first you'll notice is the huge selection of floor plans. Just take a really good look at how you travel and what your true needs are and then buy the floorplan that fits those needs the best, be it front living or the more conventional rear living or rear kitchen models. Even a bunkhouse; we actually would have gotten a bunkhouse before a front living room for how we use our 5er as it would have given us more "customizable" space.