I said two way for a reason though.
Cousins was 7th in the league in rim protection amongst those who faced 8 or more FGA per, he held any shots in the paint to 47%.
He held all post up attempts to 45%.
Held the roll man on PnR's to 30%
He held any isolation plays to 28%.
So yeah he's definitely a better defender than Marc was last year if we talking full body of work.
Real +/- which is a better indicator of player impact, also agrees.
Boogie is only behind Bogut defensively and behind DeAndre and Marc offensively.
Marc is 3rd offensively and 20th defensively.
Boogie had 10.86 Wins Above Replacement in 59 (!) games compared to Marc's 9.68 though he played 81 games.
So yeah, Boogie is the best two way center in the league currently.