Premium vs 708A for SD2.9+

Ok, I figure this has come up from time to time.
I’ve searched around, but I haven’t found a solid answer

Which drive does a better job of backing up SD 2.9+ titles?
I’ve got both…

I have read that burning @ 4x yeilds the best results.
Is this true? Or can I burn at 8x or 16x with the same results?
Also, which drive?

Thanks