The main advantages of a 5th Wheel over a travel trailer are more stability during towing, a more spacious interior and a shorter total length of tow vehicle and trailer together. 5th Wheels also have larger tanks and more storage space for extended trips.
The 5th Wheel hitch sits inside the bed of the truck, providing more stability over a bumper hitch and holding the trailer steady at high speeds and during inclement weather situations, such as high winds, where a travel trailer will experience swaying. The 5th Wheel hitch allows a truck to tow a heavier trailer because of where the weight is centered on the truck. The position of the hitch is also the reason for the reduced overall length, and for allowing a wider turning radius due to the position of the pivot point when turning. This makes a 5th Wheel easier to maneuver in tight spaces and in corners, and easier to back into campsites and driveways.
The height of the trailer and raised area above the bed of the truck give the interior both higher ceilings and more floor space than a travel trailer of equivalent length. 5th Wheels are often more luxurious inside and offer more high-end features than travel trailers, depending on the price point.