No regrets going from a 31'OAL TT to a 28' OAL 5'er. Same exact sqft according to brochure specs. But the floor plan allows for better living. More room in the bedroom, less in the living rm kitchen area. But for two people it's just fine.
As far as the steps go, we have 3 steps going in and 3 steps going up to the bedroom. FWIW our last TT also had 3 steps to get in. So that's a wash. I really doubt you will find anyone that regrets it. Sure over time when people get older those extra steps may be a hindrance. There's a reason you see more people full timing in MH and 5'ers. Better floor plans, higher ceilings and larger bedrooms. You get more sqft in a 5'er for the same OAL. A 5'er is actually shorter when hooked up than a comparably OAL TT. Towing is better. Hitching is easier, maybe not all that faster, but no spring bars or hitch head to take off every time you park. I leave my 5th hitch in the truck all the time unless I need the bed for hauling bigger stuff. No safety chains to deal with. No sway control to work out. More storage in the 5'er which means less stuff to go in the truck, which means less stuff that needs to be packed and unpacked.
As far as renting a fiver combo, that may be a tough one to do. I know they rent trailers around here, but have never seen a 5'er for rent. Most people don't have a 5th hitch just sitting in there truck for no reason. Most trucks have a receiver which allows a WD head to be fitted easily.