My friend who owns 14 classics (7-Pontiacs 7-Vettes) uses Hecock. The only reason, if you have a "collection" of cars, they offer a complete blanket policy unlike any other on the market. So, unless you have a collection of cars, Hagerty is a great company. Most important thing when dealing with classic auto ins. you need to be sure that your policy is an "AGREED UPON VALUE" policy and NOT, repeat NOT a "STATED VALUE".
My above mentioned friend is a classic car appraiser for more than 30 years now and has shown me exactly how stated value policies work and how the owner of said policy WILL get screwed in the event of a total loss. Same is true if you have your classic on your regular auto ins. policy regardless of what your agent tells you and that is a fact.
I've seen first hand the court cases my friend has been called into and also the results. He has been used as a paid witness/professional for both sides and can tell you story after story of folks like us who have been screwed time and time again by the ins. co. with policies other than "Agreed Upon Value".