Modular, I think there is some confusion here. To be clear, I an unable to restore my new iPhone 6 from my old 5C. I backed up my 5C both in iCloud and iTunes. With respect to iTunes, when I plugged in my new 6, I had to update iTunes. The apparently update killed my 5C backup. It is gone. The tech at the store that I bought my iphone 6 told me that this was a common problem upgrading to a new phone. An Apple tech also told me the same so appearently it isn't just me.
As for iCloud, my new 6 won't sync up with it. I followed the instructions and did everything I was told to. As if turns out, I an Apple Support tech told me in a roundabout way that I cannot completely restore the system on an new phone from an older one. Yes, many of the settings came through but it would have been really cool if my photos and music were preserved too! At any rate what I inferred from my conversation with Apple is that, in some cases, you can only restore an Apple device from a backup made from the same device.
Moving on, the latest version of iTunes does not have a Sync Contacts option. ***!? No matter, from my experience, iTunes is unreliable when it comes to properly synchronizing contacts. For example, it randomly duplicates the same contacts on my iPhone but does not add them to Contacts on my Mac. in other words, the sum check is faulty so backing up contacts on iTunes (and probably) iCloud is a risky proposition. In this regard, when I create a new contact either on my iPhone or my Mac, I email the VCF file and download to add to whatever machine. Yes, this is a clunky way to backup but it's the only reliable method I know of.
Back to the Apple tech, they suggested as workaround, to use Google Drive for photos and music. Again, I inferred that this was because iCloud is unreliable in this regard. I don't know if you ever seamlessly upgraded from one iphone to another via iCloud or iTunes. If so, good for you. If iCloud and or iTunes fails for me, I could care less about how it works for others. It is a binary thing for me. Either it works or it doesn't' work.