If you buy and open trailer you will only need one trailer. The open trailer can haul things that an enclosed can’t like piles of dirt, gravel, swing sets, tractors, implements for tractors etc..
Ive hade my open trailer for 35 years and I have used it for just about everything besides hauling a car.
one thing, put a winch on it you will hardly ever use it, but it will be the best money you ever spent when you need it…