The 5X isn't large. Wtf. Especially if you've ACTUALLY been using large phones.
It's weight isn't much off the OG 5, has way better battery life, WAY better camera, fingerprint sensor, punchier display, and response is speedier. Bezels could be smaller, but it's a worthy tradeoff vs old N5 for the improvements. It's still significantly smaller than a N6 or N6P.
I say if you were considering the Moto X Pure, the OPT, or Z5C then you absolutely should consider this phone as well. I've done a 180° on it myself anyway.
Now between it and the 6P, it just comes down to size preference honestly. If you can manage a bigger device, then go 6P honestly. If size is critical, seriously consider its smaller brother.