I live not too far and camp at the shore a couple times a year. I've never camped at Assateague and just don't understand why its so popular. I've visited friends who were there and it looks miserable! The national park has no electric and you couldn't PAY me to bake on that beach with all the bugs and no AC. The state park is better, but I just don't understand the appeal.
Cape Henlopen State Park, on the other end of that beach strip in Rehoboth is MUCH nicer in my opinion. Full hookup state park, surrounded by pine trees so you have shade in the summer, easy access to a gorgeous beach area, easy access to Lewes (beautiful Victorian town with some shops and restaurants) and about 20 minutes to Rehoboth Beach which is a very nice beach town with stores, snacks, restaurants, breweries, outlets, etc.
Clearly I prefer the Delaware beaches to the Maryland side.