I prefer a Diesel over gas for towing.
Case-in-point.
I acquired my current Gulfstream 232 and it weighed in at 10,100 Lbs. at the Cat Scale. I had a 3/4 Chev. 454 circa 1998. It pulled it OK, but got 8 MPG and wouldn't stop it.
I bought a 2007 Dodge Dually Diesel and couldn't be happier. Tows fabulous, stops great and gets 9-11 MPG. Far better in every way than the gas Chevy. I have had to have one transmission fix, some computer adjustment-reset or something. Other than that it has been perfect for 89000 miles.
I do agree with Grouper Duper that it is not practical for a daily driver. I also concede that for smaller boats a Diesel is not necessary, as gw204 said.
I do believe that given a similar towing load no matter how big or small, a Diesel will outperform any gas engine.
My needs are totally met by my Dually and my 1999 Toyota Corolla for everyday driving. I will not buy another gas-powered pickup.