Both Apple and Google scan your cloud synced files. Neither of them claim to scan your local only files. So the choice is rather pointless as they both hold the same position.
What do you mean by this? I use Google photos on my iphone and it seems to work perfectly fine. I'm assuming you are talking about background sync but I just checked via the web version and my photos from yesterday are all there so it seems that background activity is allowed while plugged in since I have not opened the g photos app in a while.
