I'm guessing you read the comment about the truck affecting your ride more than the trailer from another thread; don't believe it. Road shock from your truck has to go through the truck's tires, and is damped by the truck's shocks and springs. Your trailer will create bouncing forces (up and down) and chucking forces Fore and aft. A 9,000# trailer will have about 2,000# of pin weight bouncing around back there. A solid joint hitch (Andersen, B&W, Curt, Reese, Pullrite) will very efficiently hook that bouncing and chucking pin to the frame of your truck with no give, which is bolted to the cab, which is bolted to your seats. The truck's suspension isn't even a part of the energy path.
Consider also, due to a higher hitch angle and other factors,, shorter trailers sometimes chuck worse than longer trailers. Don't discount an air hitch because you have a relatively lighter rig. Case in point me. 9,000# dry trailer towed by a 1 ton dually. Should be a piece of cake right? Chucking nightmare with a solid hitch. I changed the shocks to Bilsteins, added air bags - nothing. Trailer Saver air hitch to the rescue - comfortable tow now.
Sad part is trailer generated forces differ widely amongst trailers and it is hard to tell until you hook it up. That is why you will get a bunch of differing anecdotal information. If you are buying a new truck and new trailer, an air hitch is a no brainer as the cost will disappear relative to the other costs. Towing pleasure will await.