What truck did you get, and what is the aprox tw of the trailer? As 1oldtruck mentioned, caps eat up payload. A 1500 truck w/ aprox 1500 lbs of payload and a heavier trailer can easily put you over the gvwr, and push the limits of the ra! Weight adds up very quickly as a lot of us have learned.
We had this exact situation with our '10- 1500 Silverado 4x4: 1550 lbs payload, 920 lbs tw, cab high cap, spray in bed liner, mud flaps, step bars, WeatherTech floor mats, 4 bikes in the bed, with my wife and twin 10yo boys, we were over the gvrw by up to 200lbs!
For us though a cap just seems to work better which is part of the reason we now have a 2500HD. We have a utility trailer to haul larger items when needed. And more room when heading to the cabin that is in the bush up in Ont. It's boat or snowmobile across the lake, so everything is packed in rubbermaid tubs for a dry adventure across the lake!
Good luck deciding!