The biggest benifit to running the Marine stuff of any product is in salt water environments. If you are in salt water then it is a must in my opinion. If you boat in salt water, I think the automotive stuff works just fine. I have been using the auto stuff for years without issue, but I'm in Ohio, no salt water.
Most decent product JL being one for sure have a good to allot of moisture resistance as most trunks, especially old school cars are just as moist as as a boat!