The scandals they’ve had in the past didn’t seem to indicate they’re significantly better than Google.
My understanding is that it all boils down to Apple saying that they are better than Google (what else would they say?), and there’s literally no proof, because everything is not just closed source but also guarded very tightly.
You have to take their word for it.
Apple’s also got a lot of publicity out of the San Bernardino incident, however, the phone was decrypted anyway. From Schneier’s post, the way I understood it, even the cryptography must be pretty weak, as it was brute-forced.