I recently went through a process of evaluating insurance when I changed boats. I priced a number of policies. I found that companies which are in the marine insurance business, rather than general insurance companies that happen to write insurance seemed to have the best prices and were the easiest to work with. After talking to a farily large number of insurance companies found that Jack Martin in Annapolis and BoatUS had the best deal. Jack Martin was far and away easier to deal with and seemed to understand how to work though the issues of insuring an older boat far better than BoatUS. The Underwiters were clearly familiar with dealing with older boats and thier associated issues.
BoatUS has insured my boats for close to 18 years and has provided reasonable rates and quick settlements in the few minor claims that I have had. Getting through the Underwriting process at BoatUS was a royal pain in the butt, and I eventually got sick of dealing with an underwriter who clearly knew nothing about sailboats or dealing with customers. I eventually bounced my way up to his manager and it got very much more reasonable from there.
Both companies (and the bank) required a full purchase survey. I went with BoatUS in the end because they were willing to insure the boat during shipping on a truck as a part of the policy and Jack Martin had an extra for that coverage. BoatUS also included a bigger towing coverage. That said, in hind sight, when I finally ended up with an apples to apples comparison, Scott at Jack Martin was actually pretty even in cost and was much easier to deal with.