I agree with most of the comments about the trucks, especially about a 15,000 lb trailer being pretty big for even a 1 ton. If you add the approx. 7500 lb weight of a one ton dually with 4WD to your trailer, you are at or above the limits of all the trucks I know about. At up to 25% of the trailer weight on the pin, you are looking at 3750 lb which will pretty much max out any 1T.
Also, IMHO if you are going to tow, the manual transmission is the way to go. I know that the Allison is an awesome auto tranny, but I still prefer the control I have with my manual six speed (Dodge 1T DWD 4X4 CTD).
John B.