It's really a weight issue and the length of the unit itself. I went from a 27' Safari to a 31' Classic slide out. Is one easier to tow than the other? Well there is a obvious weight issue which amounts to 2,000 lbs more weight. Yep the 31' trailer is longer so I have to take that into account. Neither of which in my case makes one more difficult than the other. The key is the tow vehicle and I can guarantee you that if I had been using my old half ton van, it would have been a much more noticeable situation and I'm sure ease of towing would be a much more clearly defined issue.
Both trailers were towed by the same 3/4 ton 6.0 liter 4.10 axeled GMC van. Difference in gas mileage? Maybe one mpg.
'04 Classic 30' S.O.,'03 GMC Savana 2500,'14 Honda CTX 700