7000 lbs. is the max on the Dakota, 9500 lbs. with the long bed F-150s, and as low as 6000 lbs. max depending on what trim level.
I'd go with the Dakota if it was me, mainly because I'm a Mopar fan, but some of the F-150's have a lower rating than the Dakota. Either/or, you'll be fine with either of the two, so why not just drive both and see which one you like better?