Restore - Difference between erase (iPhone vs iTunes)

I'll offer an opinion for what it's worth:

Let's first consider the restore from iTunes method. If we compare this to "erase all content and settings" followed by a restore from iTunes backup, I would say the difference is the restore from iTunes combines some steps for the user, so they don't have to execute each individually. Basically, iTunes restore packages several steps together - erase, then restore from backup.

A restore from iCloud has a much harder time doing this packaging, as one must first erase all content and settings to even be offered the option to restore an iCloud backup.

Finally, there is restore as new. There are two ways to do this: one from iTunes, and one from erase all content and settings. So I think the iTunes method is just there for completeness when choosing an iTunes restore, for the person may wish to restore as new, or restore from an iTunes backup.

Anyway, bottom line is in my opinion, there is no technical difference between results for any specific "restore from/as ...", only differences in packaging how to present the questions to the person doing the restore.

I've always believed from what I've read in other posts that Erase All Content and Settings does not erase the iOS. So, once at the Setup Assistant screen, if you set the device up as new, it just uses the existing iOS. To actually Restore to Factory, one can only do that via iTunes. It seems that the support document supports that theory, since it only shows restore to factory by using iTunes.

ManSinha, thank you for continuing the dialog on this, and maybe both of us can get a better understanding of the process of both iCloud and iTunes when it comes to a Restore to Factory.

Erase All Content and Settings, does just that, it does not replace the iOS. A restore through iTunes does replace the iOS.

From wjosten, see the helpful reply: Does "reset and erase all content" update iOS?

Good points about "Erase all content and settings" not updating the iOS.

I have always manually done the iOS updates before erase all content and settings, so I personally failed to consider this.

I even did this the day iOS 9.3.1 came out, which was the day I got the new iPad Pro and sold the iPad 3 it was replacing.