Wouldn't that depend more on your carrier?
But I'll offer my experience anyway: I'm a Galaxy Nexus owner on Tmobile, and call quality is great either via headpiece or speaker (both ear and loud speaker). The only time it isn't clear has to do with the carrier, like if I'm deep inside a building or something and my reception is obviously not ideal. Everywhere else where I get service, the quality has been great.
Samsung is notorious (I think? Not sure how widespread this is) but having reception issues with their devices. I haven't experienced it myself, per se. But regardless, the Nexus 4 is made by LG so it'll be a different story, for better or worse.
Hope that helped some.
I would say no. My iPhone had great clarity during calls. My Vibrant wasnt as good and my GS3 is good. LG i have no idea how good their phones are but im going to find out...though a bit later. Perhaps in late December. Im really hoping they announce a 32GB version.