I have the exact same decision this week between Moreno and Decker in a PPR league.
My starting RB's are usually Richardson and Forte. I was prepared to sit Forte and start Moreno instead (easier matchup, Forte's injury concerns, Bush vulture). But then I chose to remove Decker from my flex and stick Moreno in there, starting all 3 RB's.
So yeah, Moreno over Decker.
Remember people, we're not saying Decker sucks IRL. This is FF!