Your question is very open ended, so I am not sure you will get any answers that would really help you make any kind of a decision. FR has many lines and the quality varies sometimes greatly across those lines (Brands), I am sure there are "quirks" with many TT depending on your type of use and idea of what and how a TT's area (lets say kitchen) should function from a movement perspective.
I think you'd get a better discussion if you pick one or two TT and ask for the owners of those units to respond. At least that way you could work through say your top five choices that may meet the needs of your parents, as well as get input from others around their age that maybe using one of the options of TT you had in mind.
2011 GMC 3500HD 4x4 Crew DRW Duramax
2012 Sierra 365SAQ
2006 Police Roadking FLHPi