Sturm is a Packers fans so there may be some bias here. Having said that, I think it's a wash between Beasley and Cobb. There are somethings each does better than the other.
This.
At this point in Cobb's career, Beasley is a bit quicker on those really short routes.
At his peak in Green Bay, Cobb was better than Beasley's at his peak.
In this offense, Cobb provides more in terms the overall impact.
Beasley's lack of threat outside his niche area made it easier for defenses to cover other players.
The Beasley / Witten Combo in 2017 was very limiting to the offense. The areas on the field they were a threat were too similar.