Positives: more storage, pulls waay easier with no sway, (even when that 18 wheeler passes you), easier to maneuver/backup. solid hitch lockup (no swaybars, or leveling bars to contend with). Usually built stronger with stiff frames. Usually storage tanks are larger. Tend to be more stable when set up. Provides justification to buy nice truck.
Negatives: Requires a nice truck, heavier, almost always a 3/4 ton truck at a minimum with diesel preferred. Hitch takes up much of the truck bed. Carrying bicycles can be a challenge, depending on use of rear of rv. More expensive, usually 25% - 50% more expensive for same living space.
Some of these are not absolutes and are just my own opinion/perception from having owned both types.
2016 Ford F-350 Lariat CC, 4x4 SRW. B&W turnover with extender. 2015 CC Silverback 29RE, fitted with Reese Goose Box. Amateur Extra Class K5TS, 2016 nights camped 16