If you were to ask me this ten years ago, I would have said Mozilla. 

Today I prefer Chrome for 100 % of my computing. Why this is, is very simple for me. 

Chrome makes it easy to save passwords, bookmark pages, add nice extensions, ect.

You can perform these operations with Mozilla as well, but Chrome syncs very nicely with your google account, as well as your devices that are connected to google. For this reason, Chrome has become the easy choice for me, due to convenience.

If you are more privacy oriented, I would choose Mozilla, because the browser is very customizable, and in my experience, modifying the browser config is quite easy. 

I hope this answer helps!