...And which gives you a modal warning box that starts "Heads up! This will delete n original photos and videos from your device". And will only proceed if you click an all-caps confirmation button labelled "DELETE".[0]
That's hardly comparable to Apple deleting things automatically, silently, with neither warning nor confirmation.
Even with the warning, people assume that backup means they aren't losing anything, and can get back the original pics whenever they like. In fact, image data is being lost here. You can never get back your original photos, only highly compressed smaller sized JPGs that will look OK on a mobile screen.
There is an option when you turn on Google photo to backup "High Quality" (Unlimited) or "Original" (with limited capacity, I think it uses Google Drive capacity but am not sure)
That's hardly comparable to Apple deleting things automatically, silently, with neither warning nor confirmation.
[0] http://www.androidpolice.com/wp-content/themes/ap2/ap_resize...