Who is more valuable ROS: an emerging WR or a DST?

I have an open spot on a playoff-bound roster and can secure either AD Mitchell/Vele or NO DST. My WRs are McConkey, Pierce, JSN. My current DST is CLE. My bench includes Neal, Nix (starting Brissett), Rodriguez, Vidal. Do I snag NO for a juicy week 17 (vs TEN, while CLE faces PIT that week), or secure a 4th WR who is a potential up-and-comer?