Schottenheimer said they were "neck and neck" so $2.5 million guaranteed would tilt that scale especially if he signed with another team as a free agent if he cleared waivers.
I get the emotional factor you have with this, but this was not about which is better or worse, but simply a likely reason why the Cowboys made the decision they did when they needed the roster spot and were forced to choose.
They can still bring Milton back to the PS if he clears waivers and wants to return.
If they had done it in the reverse order, then they risked paying $2.5 million (money and salary cap) to Howell to play for another team.