I use a broker. He covers several different companies and has switched my provider 2-3 times based on rates. He has also jumped in and dealt with claims issues for me. When we first bought our boat, he walked through a couple options for me with different providers and found me insurance that is cost effective and offers some good additional benefits as well. It definitely keeps me from changing, though I have priced out options from other parties.
2016 Moomba Mojo Surf Edition
2000 Sharpe Houseboat 70x16 (Lives at Lake Powell)