One is currently on the roster for $13M the other one you have to trade away your franchise player just entering his prime and then give a max deal too. The differences in their production are negligible.
In the playoffs PER36...
Last season...
Herro: 17.9 points, 5.5 rebounds, 4.0 assists on 41/23/92 splits
Clarkson: 22.2 points, 4.0 rebounds, 1.7 assists on 55/38/89 splits
Over the last three seasons
Herro: 17.1 points, 5.4 rebounds, 4.0 assists on 41/32/90 splits
Clarkson: 22.4 points, 3.4, 2.0 assists o 45/35/94 splits
25M a year is not a max contract and you’d be getting tons of picks. Would you rather pay Brunson or Herro if you had to choose?