Come on guys. Anthony Davis is extremely versatile on defense and can defend pick and rolls much better than Cousins. He can guard multiple positions, has elite length to alter shots, and has a great vertical. Cousins can not guard the PR like Davis, cant guard multiple positions, and is not as versatile. Cousins is roaming around the inside the whole time in the paint. Not saying Cousins is bad defensively, I am just stating Davis is much better at defense but Cousins is definitely underrated defensively.
Actually while that's the story often pitched, the numbers haven't supported the idea that Davis is better at all than Cousins on defense right now (we'll see about the future), and ironically some of that is because of the very things you list. Cousins has emerged as a rock. You aren't moving him, you aren't taking advantage of him, he makes very good rotations and hedges inside, he leads the league in charges every year. he's got quick and strong hands, he's the best defensive rebounder in the game. He owns the middle. Comparatively Davis flies and flutters about. Davis can indeed roam. Has the insane wingspan. Can be a factor on any off the ball play in the game (much like WCS in all likelihood). But he's not stout. He doesn't like to stand in there. The very best thing you can do to him is drop a shoulder into him, muscle him. He's a swooping disruptive factor throughout the game, but he's not a rock. Its the same story as his offense. Its pretty. But is it dependable when things get tough? Last year the impact numbers comparing the two are inconclusive at best. I would expect this season for a +/- gap to emerge with Cuz backed up by Koufos and Davis still backed up by Ryan Anderson, but that's not going to change the underlying dynamic.
This past season, these were the Per36 stats and various defensive tracking stats and metrics:
Per 36:
Cousns 1.6stl 1.8blk 10.1DReb
ADavis 1.5stl 2.9blk 7.7DReb
Opp FG% at Rim:
Cousns 47.0
ADavis 48.6
Opp FG% Differential*:
Cousns -3.4
ADavis -6.2 (6th)
Defensive Real +/-:
Cousns 4.71 (4th)
ADavis 4.20 (7th)
Defensive Rating:
Cousns 101
ADavsi 100
Defensive Box Per Minute:
Cousns 3.3
ADavsi 3.0
* stat on nba.com I am exploring. Seems to get too many aberrant results -- #1 guy with major minutes? Nate Robinson. But if you set aside the Nick Young appearances etc., basically all of the league's good defenders do well at it. Might be a way to express the point about Davis being versatile and able to guard all types all over the floor. 5th was Draymond Green, 6th Davis, nearly identical elite numbers. Cuz at -3.4 was about #30-40 in the pack of good defenders. Gobert was -3.9. Duncan -3.2. Wes Mathews, Arron Gordon, George Hill et.c, all -3.2. Of course Carl landry and Quincy Acy were also right there, and so was Will Barton, so not sure I would lead with this stat.
In any case once you set the hype aside, its a damn hard argument to make that Davis is on another level than Cousins defensively. Can't do it with real numbers. Can't do it with metrics, on-off, player tracking numbers...its just not there beyond media getting excited by A.D.s shotblocking. But thing is that Boogie did well as a shotblocker last year too, and on top of that he adds an almost unique factor by leading the league in charges drawn. Something most bigs do almost none of at all. And a charge drawn has to be considered right up there with and maybe even superior to a blocked shot. I prefer blocks because they intimidate. But a charge drawn not only automatically gets you the ball back, but it puts a foul on the other player/team too. Its a real useful play, and Boogie is the best in the league at it.
Charges Drawn:
Cousns: 34 (#1)
ADavis: 1
Now as mentioned, if a charge taken is at least as valuable as a blocked shot, what if we just added those 34 charges to Boogie's block number to get a more accurate read at "defensive stops" if you will. All of a sudden those per 36 numbers become:
Cousns 1.6stl 2.5blk/chrg 10.1DReb
ADavis 1.5stl 2.9blk/chrg 7.7DReb
and now what do we think? We'll I'll tell you what I think: Davis has the obvious physical tools, or the physical tools we always go gaga over. The length. But Boogie has the strength, toughness and smarts/saavy. He's kind of a basketball genius you know, and physical power and league best hands are great traits to have too. Once he got some coaching and set himself the goal of learning defense, he's learned how to play it and then some. Because of the preferred super-length tool Davis likely has the most high end potential. Boogie is not especially tall for a center, not a huge leaper. But right now Cousins has made himself into one of the league's more effective big men defenders doing it his way, as always. And its a hard argument to make on anything other than hype/narrative that Davis is vastly superior. Its not there in the numbers at all.