We have had our fiver going on 16 years now, it is a 27' ,single slide unit. For almost 95% of our trips, this size has worked out for us, but on those long extended traveling trips, that last 8 to 12 weeks, we could use more living area. But that smaller size has it's advantages. In some Federal and State camp grounds.You would have a hard time fitting those 30 foot plus units into some camp sites.
Thus, if staying in one spot for extended periods, get the 30 plus unit, but for beating around the country, stay small. Hitch, we have a manual slide hitch, very seldom do we have to use that feature, and we have the 6'6" bed.