I've owned a few of both over the years and their apples vs oranges in upkeep IMO.
My current 5er weighs 11200 lb with 2200-2400 lbs on the trucks rear axle. With 11200 lbs getting started is harder on the truck. Same with getting stopped even with a exhaust brake on the Cummins.
As mentioned the trailers tires/wheels/axles/springs/bearings have to be maintained along with the hitch in the bed issues (removal/upkeep). The trailer has a lot more issues from body/frame flex with frame cracks and cracks in the exterior.
I could go on but you get the picture.
IMO the biggest decision you will have to make is interior room. You either need a 8' wide x 8'-16' long box or a 8' wide x 25'-40' long box to stay in and move down the road and maintain.