Granted, I've only had the 6P for a couple of days... And I had the Nexus 6 shortly after launch...
I can really only point to one thing that the Nexus 6 did better : Ambient Display... As there seems to be a bug in the 6P right now causing it to fire inconsistently.
That's about it so far. The 6P has, so far, really impressed me. Well built, feels nice in hand... The 6 had a kind of janky haptic feedback, more buzz that vibrate. The 6P has a subtle thump with a quiet, xylophone-like bong... That's a little touch, but I helps the 6P really feel premium.
Performance wise, the 6P really feels agile. Screen transitions, scrolling, etc. It doesn't trip up at all.
Now, tomorrow's commute will solve a couple of questions. It's a kind of a stress test for the mobile radio.. The 6 was able to stay on near the entire drive that has since signal challenges... So I'll be able to see how well Huawei and the 6P's antenna array handle things.
This is one hell of a phone though, I don't need more time to see that.