If I had a family of 4 I would go with a trailer (or a Tiger!) unless you have a dually and are ready to go with a big truck camper. The trailer can be at home packed and ready and it just takes minutes to hook up and go.
My truck camper stays on the truck most of the time so there is no hook-up time for me.
The BIGGEST plus for us with the truck camper is increased mobility and ease of driving vs towing something. I can pull into virtually any parking spot/lot, gas station, do a U-turn on a fairly tight road...I'm just driving a truck.