They are both good options but very different. We have had both - sailboats that we raced on Lake Erie and a small Sprinter-based class B van. When we retired we finally gave up the big sailboats partly because the racing season impinged on our travel plans and partly because I finally got tired of racing. So now we have a canoe to maintain our interest in being on the water together with the RV.
Before you jump into either a boat or an RV, perhaps you should sit back and think about what kinds of activities you enjoy doing. Then contemplate whether either a boat or an RV will provide a means of doing those things. There are a lot of hassles with either boats or RV's so neither will be worth while if you don't get something special out of it.
I agree with your concerns about going to a crowded RV park and being close to neighbors that you might not like. The answer to that is to use the RV as a base to live in and to spend your time doing the things you enjoy. For example, we like the outdoors and travel to National Parks or other places where we can indulge our interests.
Personally, I suspect that I would get tired of motorboats very quickly unless I was interested in either fishing or water skiing. Driving around in circles on a little lake can get old in a hurry.