OK, that is really all I am basing it on, 2016. They had a good 14, a disastrous 15 and they needed a quick rebound and which player could immediately impact the season and the one missing ingredient from 14 was the RB. And the Cowboys have a follow the ball GM.
I am not a fan for the future, I am only in this season and what happens in 2018, just as I was in 2016. I was on Zeke from the get go for one reason only, he was the best immediate impact player I saw in the draft. Bosa and Ramsey would have both helped but taken this team to 13 wins? Nope, and all I cared about was that season. Like now, I don't care about 2019 at all.
When I was younger and before this disappointment/surprise teams thing was the norm, I could look 3-5 years ahead and actually cared about the pretend season because those players were the future of the team. Now, there is only now.
If you are weighing the two players/positions as a longevity and contribution comparison, then I would have to give the nod to the CB based on the averages. But, if I am looking at immediate impact at a position, none better than RB.