Bucks fan here...the Suns are a horrible matchup for the Bucks and are my pick for The Finals.
Milwaukee gives up a lot of good looks from 3 and Phoenix does a great job spacing and getting.the ball to shooters while Paul & Ayton have formed a nice pick and roll combo. If the Bucks play drop coverage, the Suns have two great midrange shooters in Booker & Paul and Ayton has done a great job hitting the offensive boards.
On the other side of the court, the Suns have something the Nets and Hawks struggled with...a defender who can matchup with Khris Middleton. Bridges defense is underrated and he'll make Middleton work for his points. Same with Paul on Holiday. When Giannis plays the Suns also have Crowder, who does a good job making him work for his buckets as well (see the Heat victory last season with him).
Add in home court for Phoenix and this series looks more like a Suns in 5 type series than it does Bucks in anything. Hope I'm wrong, but I think this coin flip between the two teams doesn't end with the Bucks landing the top prize this time around (See - Alcindor).

If the Bucks had a healthy Giannis and Divincenzo I'd go Bucks in 6, but that's just how the 2021 playoffs have been.
When the Bucks play PJ Tucker the Suns will be able to rest Booker or Paul on him. His shot hasn't been there of late and offensive rebounding has been his contribution to the Bucks offense. Meanwhile Holiday will get worn down guarding Paul/Booker and Middleton may end up on Booker a lot as well. Bud seems to have two decent options: play Connaughton more than Tucker or go big with some minutes with 3 of Giannis/Lopez/Portis/Tucker and try and bludgeon the Suns inside, get Ayton in foul trouble, etc. If Bud plays Tucker more, I wouldn't be shocked if he's matched up with Booker a bit and they switch everything. Making Booker the guy who they make hit a ton of mid-rangers to beat them.
Best best for Milwaukee is attacking the rim to get Ayton in foul trouble and turning the series into a rock fight. The Bucks still have to push for easier baskets in transition, but they have to take away the wide open 3's and outrebound Phoenix to have a chance. Can the Bucks play big and take away open looks from outside? I'm skeptical. Which means we'll see the Bucks play small at times and get slowly picked apart. Sad bromingo trumpet.