Pixelmator Pro is my own choice – Pixelmator is almost as powerful, but the team has just essentially moved from growing that into Pixelmator Pro and it seems clear they intend to support and develop that for years to come. (And they've said they plan to raise the price to justify future work, so that might be a hint to buy it soon if you're going to.)
(That said, I know Affinity has a good reputation among its users – a bit more of a technical details flavour to it, whereas Pixelmator Pro seems to strive to be as "Mac" as possible.)