The campground is split into 2 sections: one is north of the Indian River Inlet and the other one is directly south of the inlet. When I was last there in 2016 or 2017, the north end was far more modern than the south end. The north end had concrete pads for each site and a nice modern bath house with a laundry room. The south end was much more rustic with sand/gravel sites. They may have made improvements to the south end since I was last there. We've stayed on the north end twice, for a total of 3 weeks, and we loved it. You can easily walk to the beach, the marina, Hammerheads Dockside restaurant, and the Burton Island nature trail. The beach is probably less crowded on the north end than it is on the south end, which has more public parking and beach concessions.
As far as which site it best, that really depends on your rig and your family dynamics. We stayed close to the playground so our daughter could easily run back and forth to play. We also enjoyed being near the coast guard site and hearing them play Reveille every morning. I think they also played Taps at night. There are other sites closer to the water with nice views, but those tend to go fast.