Your BEST mpgs per a fellow that pulls RV trailers for a living. Will be the airstream and mid sized 5w withOUT a front bedroom slide. The Glendale Titanium 5W is another that gets better than ave mpgs. Travel trailers with aluminum sides are generally speaking the worst. He always gets better mpgs with the 200-500 lb heavier same models with the smooth fiberglass sidewall vs an aluminum sided one.
Issue some of us have like myself with 5W's, I use my truck as a contractor, pulling multiple trailers that are bumper pulls if you will. I have to also take off a lumber/ladder/pipe rack off the truck to install a 5W hitch, ea time I want to pull a 5W trailer. Not happening!
I also get way more use of the bed, along with I can haul easier a canoe, kayaks, small topable boat if need be too. Or some haul golf carts, off road bikes/quads etc in the bed with out having to go to a rear garage style trailer...
At the end, there is in reality, no true right or wrong RV trailer. Only the one that YOU, most important, SPOUSE likes, if spouse does not like it, your screwed no matter all the other positives.......
Get the one that works for you! I was very happy pulling my TT with souse and 4 kids in a mid 20' TT thru snow and ice, sleet, sun etc over 12 years and 120K miles, not to mention most useage was December to April as a ski hut. Yep, hauled to local area dang near EVERY weekend! Don't let a bit of that winter white stuff scare ye too much either!