Photomator is significantly more capable than Photos on the iPad and iPhone: it very obviously has a more robust image editing pipeline, supports layers, has actually useful ML features, proper curves, vastly better colour balance editing, supports LUTs, has culling support etc.

Photomator on the iPad is more capable than Photos on the Mac.

Frankly I think this is an acqui-hire. I think Photomator will significantly boost the capabilities of Photos, back to an Aperture-level app. I think some of the features may even end up in the camera.

Pixelmator, I don't know. I think a whole bunch of Pixelmator features do make sense as a tab/workspace in Photos, actually, but either way I don't see Apple keeping it called "Pixelmator"; I would expect to see it called "Images" (to go with Pages and Numbers, and with photo-specific stuff left in Photos).