We ran 3 WR sets 65.5% of the time last season. 4 WR sets 1.9%. So basically usage, and depending on your other two WRs, ability to play outside or the slot.
Why some people were disappointed with the Cardinals not taking a WR higher is that AZ is one injury away from having Zach Pascal playing 60% of snaps. That is in addition to counting on Wilson to be able to play at least 81% of snaps again, and Dortch going from 38% to 60%. And of course MHJ being able to start from day 1 and play a high % of snaps.