Cyanogen is superb at present (pre-Microsoft), and looks/works just like stock Google Android on the surface. I haven't installed the Android 5.02 version (CM12) yet, but the original/updated CM11 is really good. Lots of useful features, and essential ones like Privacy Guard that don't come with stock Google Android.

The OnePlus One, out of the box, is missing a couple of key LTE bands that apparently are common in GB / EU. I forget which ones, but the Nexus probably has them. There are hacks to enable them on the OnePlus, but I have no experience there.

EDIT: Google account not required, but pretty much essential to have if you want to use the Google Play App Store.

Cheers