You go with Giannis imo. Cooper may be a superstar but at the end of the day, we just don't know. He could end up a 20ppg guy which is great but not star quality that will get you titles. You get Giannis you have 1) Giannis who's won a title with an average supporting cast 2) AD who's won a title leading his team in damn near ever stat category and 3) Kyrie, who had an amazing 2016 Finals and hit the biggest shot ever. 3 stars that are experienced and have proven to be ice cold all in their own way.
You get about 3 years to try to win with that cast, and then you can rebuild after.
I understand health is an issue, but damn near ever star player now seems to be in an injury risk. You just gotta roll the dice.