The difference between Phots and Lightroom is similar to the difference between Pages and Word. Pages is a handy app for doing a letter, for making a parish newsletter or some such. If you're doing a doctoral thesis then you need the heft and power of Word.
Photos is an excellent app for its target user, who is probably shooting with a phone and likes as much of the work in processing and managing his/her images automated as possible. This is not to say that Photos won't do other things, it will, but it is aimed squarely at the consumer market. Lightroom Classic is aimed at the Pro shooter or serious hobbyist, probably shooting RAW with a DSLR or other kind of ILC. It's much more powerful app, particularly at raw conversion.
Lightroom uses a referenced library by default, and has all the tools needed for that task. On the other hand, if you have a fondness for pain and pointless chores, the run Photos in referenced mode. Just remember you can't use iCloud Photos and Photos has no tools to manage images stored outside the package. So this is where the pointless chores come in: Everything is more work for you: You move the images from the camera to your preferred storage. Then import them. Deletions? Delete the image in Photos and then go to your storage and root out the deleted image yourself. Anything like moving your store to another disk to a new computer becomes a world of pain because - and this is where the pain really comes in: If the path to the file is broken for any reason you will need to reconnect it manually. Not really a problem if it's one photo. But if it's 10,000 or 100,00, well that's a lot of pain indeed.
My rule of thumb: If you want to use Photos don't use a referenced library, if you want referenced library don't use Photos.
You can migrate from Aperture to Lightroom Classic and also migrate from Photos there. I have significant doubts about going the other way but an app like this might help:
https://cyme.io/avalanche-photo-conversion/
