Mikal is a better defender, although his defense dropped off after taking on greater offensive responsibility. He averaged 26/5/3 with 1.8 TOs on 61% TS after being traded to the nets. JB has shown more in the playoffs but also is a turnover machine sometimes. He averaged 27/7/4 with 2.9 TOs on 58% TS. Personally, I think for now Brown is the better player, mostly because he’s a better rebounder and iso scorer. I think Mikal can easily overtake him this season if he shows more in his bag.
I think the better question is will Milan Bridges reach Jaylen Brown’s tier. JB has been playing at a borderline all-nba level for about 3 seasons now. Mika hasn’t done that.