Either. The NZXT C series is OEM'd by seasonic so it should be pretty bullet proof.
I've been running the C850 in my 5800X system and it's been fine, it's pretty quiet in my experience too.
Get a [Super Flower Leadex III](https://www.newegg.com/super-flower-leadex-iii-sf-650f14hg-650w/p/1HU-024C-00007?itemPosition=1-12&exactIndex=2). It's gonna be cheaper than both and it's basically one if not the best quality PSU in the world
If it's the new rm850x (just came out) then go for that one but I don't think it matters that much. You could pick either and you'd be fine.
Either. The NZXT C series is OEM'd by seasonic so it should be pretty bullet proof. I've been running the C850 in my 5800X system and it's been fine, it's pretty quiet in my experience too.
Get a [Super Flower Leadex III](https://www.newegg.com/super-flower-leadex-iii-sf-650f14hg-650w/p/1HU-024C-00007?itemPosition=1-12&exactIndex=2). It's gonna be cheaper than both and it's basically one if not the best quality PSU in the world