Because I have eyes...
It seems like there is more of a hope of what Beasley could be with crafty Amendola or Wes Welker-ish traits. But he really hasn't shown anything other than 15 recs on 24 targets. But my issue is he is not fast, or shifty in traffic once he has the ball, he is not a homrerun threat, he can't fight for the first down, and has no size to fall forward like a Sproles or MJD would, at the same stature. So between the two options, if you give the 24 targets to an exceptionally fast player who is shifty, is fast, can play multiple roles in the offense and special teams, you might end up with a lot more yards for those 15 recs than 8.5 yards per reception.
Right now, all of the special traits of Cole Beasley can be found in Dwayne Harris, Miles and Dez, but none of the special traits of Armstrong are in the first four WRs in terms of pure speed.