I don't think an argument can be made that one is better than the other if you are looking at team success. In spite of some prolific numbers Dak put up at the start of this season in mostly losing efforts, he has yet to prove to be a winner. At this point, Dak looks much like Romo compiling lots of meaningless stats just has Stafford has in Detroit for years. Stafford is absolutely the superior arm while Dak is younger and more athletic. Dak is probably a better leader as well.
This is going to come down to , as all things in Dallas do, to whom Jerry feels more loyal. I don't see Stafford replacing Dak. Jerry loves Dak and that is the biggest factor in Big D.