For what its worth, I upgraded my iPad Air from iOS 7 to 8, which is similar to restoring an old backup.. ie transfering settings and such, not setting up as new with fresh settings.
Only after I couldn't get the Remote App to detect my Home Sharing devices, I reset my Network Settings on the iPad, did I realize there was supposed to an option for attaching to my iPhone 6's personal hotspot, directly from the ipad without having to enable it on my iPhone. I recall hearing about this feature for the Macs many months ago during the iOS8 preview, but didnt recall it would be available for iPads. Basically a new and big benefit to iOS 8 wasn't even showing in my wifi settings prior to resetting my Network Settings. That has convinced me to never restore after iOS releases on new iPhones.
TLDR = there does appear to be real benefits to starting fresh on iOS devices.