OP: Your points are generally subjectively valid, but if we're going by the reviews, here are a number of relatively "1st-tier" tech sites review headlines. Note, I can't provide links because I don't generally post on the forums, and so I can't post links. I assure you they're there though with just a little digging

:
Gizmodo: The Android Phone for Everyone ("It’s cheaper than flagships like the Galaxy S6 and the LG G4, and I think you would be nuts to buy those over the Nexus 6P, which is a better phone")
Wired: "The Nexus 6P is absolutely the best Nexus phone ever. Hell, it’s the best Android phone ever."
The Verge: The Best Android Phone ("The Nexus was always a good Android phone, sometimes a great one, but never the best one. Now it is.")
And for a technical take, ArsTechnica: The True Flagships of the Android Ecosystem ("Every other Android phone pales in comparison to the Nexus 5X and 6P.")
It's perfectly valid for you to value the items stated in your OP over anything else, but note that the 6P beats the Note 5 (handily, I might add), in ArsTechnica's Wi-Fi browsing test, while losing in the CPU rundown. The Wi-Fi test is generally a test of display efficiency (if not quality), so take that as you will. In camera, I'd say they trade off, personally. Sound quality through headphones... I haven't seen anything stating that but I haven't seen it stated the other way. On the other hand though, pure sound quality is likely a massive advantage for the 6P. I personally don't think sound quality is likely to make much of a difference on any phone when you're using earbuds.
And you're forgetting a couple great things about the Nexus line:
- Software. Touchwiz might be (by some opinions) decent, but it's hard to argue that it
helps the devices performance. It definitely brings some advantages, but overall, most (and this is subjective), prefer stock android.
- Updates, updates, updates. The nexus 5 just got Marshmallow. That was the same year as the Galaxy S4, if I'm not mistaken. And I'm pretty sure the Nexus 4 got Lollipop, in the year of the
Galaxy S3. That's a big difference in OS updates, not to mention the speed they come out at. My AT&T S6 (holding onto it until my 6P comes in) didn't get 5.1.1 until about two weeks ago.
- Security. Semi-tied to the updates above, and kind of self explanatory.
- Other features. Always-On. Actually getting Marshmallow before April. Ambient display.
On the other hand, the Priv? OS Updates, while I expect Blackberry would do well on them, are COMPLETELY unproven. This is a gen-1 product. Software quality is completely unproven. Camera - unproven. The priv
could be a great phone. It
could be a gen-1 device that needs another year to mature. And you said you'd return or sell it if you didn't like it, but why didn't you do the same thing for the 6P?
It's perfectly reasonable for you to value some points over others that cause you to pick the Note 5 over the 6P, don't get me wrong, but I think it's disingenuous to call the reviews "less than stellar." I've already provided four that included some version of "this is the best android phone you can buy today." Others I've looked at have included CNET and Engadget. Both concluded that the 6P is an incredibly good buy, and competitive with any other option out there. I'm not saying that it's literally impossible to prefer the Note 5, but I think it's disingenuous to say the reviews were "less than stellar." I just provided 6 reviews that concluded either that it is the best Android on the market or that it's an incredibly good, first tier phone. I'd love to see a similar number of reviews from well read sites that have a less than stellar conclusion. And if they aren't well read, why are they influencing your purchasing decision?