Yup, the new X uses the 135.Did Moto X 2014 use IMX214? It uses 135 I thought? So if the N6 is using a 214, this might be a good step up.
But remember the OPO isn't THAT great in camera too. In the end the whole package matters. Sensor is only part of it. The firmware, camera module maker, etc all need to come together to give a good package.
You're right that firmware is crucial, but with RAW support in Lollipop maybe third-party fixes will be able to do more for camera output than before.