I've had all three...Trailer, Camper, 5th Wheel...so I'll list some of my pros & cons for each
* trailer...for comparable length you get a little more room; plus a standup bedroom. You also get mechanical advantage when backing up since the pivot point (hitch) is 3-4 feet behind the rear tires
* camper: unlike trailers and 5th wheels you don't have the expense of 4 extra tires (plus spares), axels, shocks, brakes, etc. You also, if you like to go to the forests and deserts and travel of rough roads have the most maneuverable RV option. But campers are small and are a pain in the ass to load and unload. If you find someplace you're like to stay, then you either have to go thru the effort of unloading so you can use your truck, or you have to pull a toad....which means tow a car or a Jeep, etc.
and new campers with slideouts are frigging heavy...and expensive. As in over two tons and 60-75K. And you either need a dually to carry that weight, or something like 20-ply tires with high load ratings. And since those tires weigh in (with rims) in the 170-300 pound range....good luck changing a tire if you get a flat
we had a Lance camper for 10 years and went all over the place, including some roads only suitable for 4 wheel drive. But again, it was either spend a night than move on, or go thru the major hassle of unloading...then loading back up when we wanted to move
* we now have a 5th wheel. It's a small one, 24 feet, with no slide-out (which adds anywhere from 1200 to 1800 pounds just for the steel). By myself I can hitch up and load the 5th wheel and be ready to roll in 5-10 minutes. A trailer takes 2 to 3 times longer, and many require a driver and spotter. Now, as I mentioned with trailers, the mechanical advantage of the hitch being behind the tires makes it easier to back up. With a 5th wheel, the pivot point is directly above the rear tires so it's slower to complete a turn and it reacts slower. You have to anticipate more with a 5th wheel.
But, there is a huge advantage if you're driving down a road with strong side winds. That trailer's mechanical advantage becomes a big disadvantage and can push you all over the road. With a 5th wheel, the wind force is blunted by loading directly over the rear tires. I've driven the 5th wheel easily (relatively) thru winds I would have probably parked the trailer in. And a camper really lifts your center of gravity so it can be unnerving in strong wind too
now, these 5th wheels that are so massive appearing when you're approaching them going the other direction is because they have full walk in bedrooms in that front section. If you get a smaller 5th wheel that has more of a camper bedroom extension, they don't have that massive front profile. Some of those monsters are 13-14 feet tall. Ours is around 10'9, and that's after I reversed the springs to lift the 5th wheel for more clearance on rougher roads. That way I mitigate the possibility of dragging the back end in a ditch of gully. It also gave me more room to add quality shocks
(speaking of which, one thing I learned, an expensive lesson, is that if you go thru a ditch with a camper, you risk tearing the back jacks off by bottoming them out on the ground...thank god for insurance)
If I was only interested in going from RV park to RV park, I'd probably have a trailer. But we rarely go to RV parks and instead dry camp about 90% of the time. I had a service bed put on the pickup (F350 Diesel) so the 5th wheel seemed the best option since I have plenty of space for camping cargo