We just went through the same decision making exercise between State Farm and Good Sam's Club (GMAC). Where we live, Sam's Club is just a few dollars cheaper, but that was not what caused us to drop State Farm. It was the difference in what is actually covered. For example, Good Sam's covers the loss of the contents of the RV up to, IIRC, $2000. State Farm does not cover contents. We happen to carry a couple thousand dollars in camera equipment with us that State Farm would not cover. There are several other items similar to that which made Sam's Club the obvious choice.
If you’re not using the RV for part of the year, you can get a lower rate. I would suggest staying with StateFarm since your car and home are insured by them too. But you might be able to get a better RV insurance quote, so keep looking around. Don’t give up!