Bucks
I just can't get over how poor the floor spacing would be with this team. The starting lineup has one shooter. Rose and Giannis' ability to get to the rim is mitigated by the poor floor spacing. Mourning's ability as a post up scorer is mitigated by not having shooting (even the year that was picked for mourning, He had Hardaway, Majerle, and Mashburn in the starting lineup to spread the floor a bit). Malone was a bit better of an outside shooter, but I think some of his scoring inside is taken away as well.
I do like the Bucks bench a lot. Tatum, Conley, Miller, Butler, and Reddick all fit this team well and were great draft picks, but I can't get over how the stars don't fit together well. They were a trade away, in my opinion.
Celtics
The more I looked at the Celtics roster, the most I thought they were the best team built together. Gasol and Gasol would be a really difficult matchup for any team just because of their intelligence and the feel for one another. Durant is as good as anyone in this draft. Nash would open so many easy shots for the Gasol brothers and stretch the floor for Durant.
I also love the other guys he drafted. Wallace could/should be a starter in this tournament. Granger and Jefferson are both versatile athletes that can play both sides of the court and score at a high level. Dragic and Stockton both fit as backups in this system. Houston and Richardson can stretch the floor on the wing. Hillario was a really underrated player during the best moments of his career.
I would have preferred that this team had one more truly elite guy on the wing with Durant, but I think this is the smartest team that fits together the best in this draft.