I know if you had a camping trailer like the Aspen Classic with electric brakes, you would need that 6 pin connector. Usually the center pin is for the electric brakes. Do you have a brake controller somewhere on your bike? Now the Aspen Classic without the electric brakes also uses a 6 pin connector but the center brake pun is not hooked up. Many cargo trailers will utilize a 4 pin flat connector but then you will need a 5 to 4 converter to make that work. And if the trailer has LED lights then you have to be careful of which 5 to 4 converter you use.
But bottom line, the trailer you use will determine what connection you need on the bike. But then again you can always modify the trailer wiring to match the 6 pin.
Confused yet?