Pick up Cohen if D. Montgomery is out, or roll with Mostert

So, I’m not putting DJ or Sony in my lineup this week, and Jamaal Williams is on bye. Do I drop Mostert and pick up Cohen off of waivers in case Montgomery can’t go, or roll with Mostert as RB2? I am playing Ronald Jones as my other RB this week.
PPR

I’d roll with Mostert over Cohen. To me the matchup is better

PPR I would roll with Cohen. It’s honestly a coin toss though. Mostert will probably do more in the running game then Cohen so it comes down to who scores. Cohen is in a tough matchup and mostert is a sneaky play with Matt Brida likely out but mostert has been hurt with a knee issue so I lean Cohen due to target volume.