Some of the reasons I haven't switched are because of the useful Photo Stream import (auto downloads all my photos from my phone upon launch no cable required) and Lightroom's import is a joke. It doesn't retain all of my albums, projects, or their sorting. Plus I don't want any kind of subscription to Adobe's services.
I'll make the switch as soon as someone has a good importer that doesn't mess up my projects and folders. Plus stores their edits.
Aperture Exporter can import your projects, albums, and folders, and I think Capture One might have something similar. But you are locked into the Apple if you wanna use Photo Stream with that, assuming it continues to be supported.
And all your edits will never be exportable, except to Photos.
As far as RAW conversion is concerned, note that Aperture does NOT have it's own RAW conversion. It relies on system software for that. It has more tools, but if one likes Apple's renderings (and it's rather subjective; see a comparsion of a bunch of converters here:
RAW Converters Comparison - nomadlens) then perhaps Photos would work. It too uses Apple's raw conversion, it just doesn't have as many tools. And recent entrants include Affinity Photo, Mylio, and probably others, as well as new tools in some of these (dehaze seems to be popular now), especially for certain adjustments (like Noiseless Pro by MacPhun).
I think AfterShot Pro still can use a managed catalog. And of course Lr can export a catalog plus its referenced files. I used Aperture for this in the same way, but it was horrible if you had to give that to a client. With an Lr catalog and its exported folders it was easier, cuz the client could just ignore all the Lr stuff and still have all the photos in their proper folder structure. And by using the file structure one could set permissions for access in file sharing scenarios.
And if you goal is sharing photos back and for to iOS, check out Mylio. It's far more powerful than Aperture/iTunes/Photo Stream/iCloud Photo Library, and far more flexible. And free for three devices and I think 5K photos (no online storage for free, but unlike Apple's apps you don't need online storage to synch). Does RAW, uses color calibration on iOS, and shares edits with Lr as well.