Trevor Bauer has no performance related red flags. Pretty much every pitcher in baseball is using something to enhance their grip, so unless MLB decides to fully crack down on everybody Bauer is going to be perfectly fine to continue doing what he's doing. Besides the alleged cheating (we have no proof, only suspicions at this point) he's produced elite results with spin rates within his typical career norms before 2020. He typically stays healthy, limits walks, provides plenty of innings, induces weak contact and racks up strikeouts. This is an elite pitcher by any measure that you want to look at.
James Paxton is a broken down oft injured starter who you can bank on missing several starts every season. He is coming off of back surgery and a forearm injury in 2020, and his results on the field were terrible. There is a good chance with a full off season to strengthen up that he will bounce back, but he is several tiers behind Trevor Bauer in the ranks of starting pitchers.
There is no denying that Bauer is a prick off of the field (sometimes on the field too, thinking of the ball tossed into the center field stands episode) but he's one of baseballs best starters. Signing this guy instantly elevates the Jays into true contender status. Paxton would be a nice fallback option banking on a bounceback season, but he's far from a sure thing to provide value on whatever contract he obtains. Bauer has a potential ceiling of 7 WAR with a good season by his standards, and a poor season by his recent standards would be 3 WAR. A good season for Paxton places him in the 3-3.5 WAR range, which is the lower range you could reasonably expect for Bauer.