Since all the rigs you mentioned use the same power train, you could pick the lightest weight of those you like. I say that only if power and speed are your priority. Fair warning, if you try to run one of these fast on our roads, it will slowly be vibrated apart in the house.
By the way, I wouldn't pick a Class A gas based on weight. My 2013 has plenty of power and I haven't had any problems loaded down and pulling a Wrangler Unlimited (4 door).
We have been up and down the East coast. We are headed out West this summer, so I will know more then. You will slow down on some hills, but you will not have to putt-putt up them. I regularly pass tractor trailers and rarely have one of them pass me on our decent WV hills.
I would pick the floor plan you like with the amenities you like on that chassis.
If you want to travel 70++ MPH while pulling a Toad and loaded down with 4,000+ pounds of stuff, you might want to look diesel. If you don't mind cresting a hill at 60MPH with some power to spare, the gasser will do you just fine.
Also, check the Cargo Carrying Capacity very closely. All Ford motorhome chassis are not the same. If you are considering a MH that weighs around 19,000 pounds, check to see if it is on the 22,000-lb chassis or the 24,000-lb chassis. That will make a big difference as to how much weight you can load and/or pull.
One manufacturer may roll out 19,000 pounds on a 22K chassis and call it good. I wouldn't.
Here are Ford's published specs on the 2015:
F 53 SpecsGood Luck