As someone that owns and uses both, I would say it depends on what you want out of it.
OS aside, there are some important differences.
My 1+1 has a much better battery life and comes with much more storage out of the box (if you have an SD card, this may not be an issue). You were asking about call quality and I can say that its... Ok. Nothing special, but not great like Lumias.
On the flip side, my 830 has a removable battery, takes better pictures, and just kinds feels more premium (if that's something you care about. The metal makes it feel expensive).