If you just want a phone that can boot a mobile operating system, then perhaps a Nexus device will do it for you. But there are other phones that have features not included on the Nexus line that make them appealing to folks.
But for practical use there are no benefits. Not even if you have a older device. The One is maybe the most beautiful designed piece of hardware I have ever seen, but other than there is not much that I can do better with the One than with my Nexus 4.
I still want that damn phone, though.
As for the price, the differential seems like it's smaller outside the US, where the Nexus is barely marketed. And since I don't replace my phone that often, even a $200 difference is just not that critical.
There is certainly issue of bloatware - but you can either delete them (with Titanium Backup) or just hide the icons (in my launcher).
I just can't get behind carrier/manufacturer cruft. I also feel that Android itself iterates and innovates faster than Samsung/Moto/LG/anyone else can on their own, so those 'extras' are not at all extras.
I'm also considering switching from Verizon just for this....
I had an HTC and the GPS was terrible, then I switched to Samsung, and it worked well (for the S2 and S3, which I had).
Since GPS performance is something that reviews apparently care little about, I'm not going to change brand, without having accurate GPS analyses at hand.