BOAT/US has both and trailer towing coverage on the road. I have very good coverage at a very reasonable price on my boat liablity and comprehensive coverage. It's an agreed upon value coverage which is one of the better types of policies.
There are other benefits to belonging to BOAT/US especially if you are concerned with the health of the waterways, fish stocks, etc. They also have good discounts on gasloine at some marinas when you are a member. I just paid my memberhsip fr unlimited on the water towing, road service while trailering, and my annual membership and it was $146.50
Just another consideration. You'll get 50 more responses waying who is better than who, but you should decide for yourself. Just comparison shop. Make absolutey sure that you understand what you being quoted when you shop for your boat insurance. Price alone doesn't cut it. Some folks get real surprised when they go to collect. I've had one problem in 20 years and had to put a claim in and it was a real pleasure dealing with BOAT/US.
Just a small tidbit and this doesn't make me an expert, but I used to sell insurance for a while some years back, so heed what I say when I tell you to really understand what you're getting.