„Really big“ means:
Those couple hundred little features android has. Ios is the best looking mobile operating system but android is waaaaaaaaaay ahead of features. Not even big features, very little things.
A couple of months ago I made a list of features I would like to see in ios 13 and added every little bit that came in mind over the weeks. I ended up with ~200 entries in that list, too bad I deleted it.
I have a big one to add on that list: give apps access to hardware. I have to carry an old Nexus5 to be able to do WiFi surveys.