Well, I think you beat me to the punch. Those are the three phones I would have suggested.

My bias lies toward the Nexus devices and their plain vanilla Android, mostly because I've yet to see any of the third parties produce anything appealing. Others on this board like the Oneplus for its security features.

I'd probably say that the Zenfone 2 is a little outdated since the announcement of the 3.

So yeah, personally I'd go with the Nexus 6P because that's the one I wish I'd gotten instead of the 5X, which I just don't think is up to snuff (too slow).