I'm staying at Wickham park right now, another very nice Brevard County campground. This is our 3rd time staying here. We camp here and walk to the adjacent Maxwell King Center for the Performing Arts, on the campus of Eastern Florida State College, where they have a wide variety of entertainers/performers.
I've stayed at LP twenty something times, but I have never stayed at Sebastian Inlet S.P. The first time I drove through L.P. I didn't like it, since we had a pop up at the time, and there was absolutely no shade. Since then I've camped there in a T.T., a truck camper, and 3 different motorhomes.
If you're a boater, L.P. is the place to go, since many of their sites are right on the water with water access for your boat, right at the site. I don't believe any of the S.P. sites have water access. They also have a ramp, as does the S.P. Many of their sites are huge, while others are pretty close together.
Long Point is packed all winter long with snow birds, so it's hard to get a reservation. During the summer, or off season, it's packed on weekends, but practically deserted during the week.
I'm sure you would like either park.