My priorities are, in order:
1) Safety - Most likely towing a 5er is better to tow due to the pivot and weight being located directly over the rear axle. A higher profile does create more surface area for wind. If it's real windy just don't travel that day, it's a lot more relaxing.
2) Quality construction. - Good and bad in both, this will just require you to investigate anything you consider purchasing. This site and product specific site provide massive amounts of information overload.
3) Ease of hitching, unhitching and set-up - I had a 31' TT for 18 yrs and now a 5er for 2 yrs. A 5er is hands down easier for me. I carry a small 2 step stool in the bed of the truck to access the hitch.
4) Overall interior comfort, storage, and functionality for FT living for one or two years - My TT allowed using a shell on the truck, lots of storage, sometimes hard to access. The TT had a single slide for the couch. I would consider a slide to be a must have for the days your stuck inside. Our 5er has opposing large slides, 14'x3'. When closed you can access everything but are in no way livable. When open the space is amazing for a RV. I tell everyone the laminate flooring in the kitchen are is a dance floor. We also have a small slide in the bedroom. Space on the bed side it tight, longer units solve this but I wanted this length so I can double tow a alum fishing boat behind. The basement has massive storage but with carpet and plumbing you have to be more careful than with the shell covered truck bed for the TT.
5) Bang for my buck - Buying a nice used unit give the most bang but will probably require some upkeep.
A single rear wheel truck will limit 5th wheel choices due to the weight carrying capacity of the tires. Gas engine duallys will take you up to 13,000-14,000 GVW due to towing limits. They'll have around 5,000 lbs of weight handling capacity. Diesel duallys have capacities far beyond what you think a pickup should be towing.
See, information overload. Good Luck and I hope you hit the road and enjoy all the many wonders you'll find.
2012 Chevy 3500HD Dually 4X4
Crew Cab long bed 6.0 gasser 4.10
2019 Open Range OF337RLS
Yamaha EF3000iSE
retired gadgetman