My wife has been using a Samsung Droid Charge for a few months. The call quality both incoming and outgoing is superb. I can tell immediately when she calls me on her Charge as it is crystal clear.
She did have an issue getting the GPS to work, but everything else on the Charge is top notch. She leaves it in 4G and it does drain the battery very fast when viewing the internet.
Samsung works very hard on quality in there other products. My daughter just purchased a new Samsung refrigerator and it is recognized as one of the very best. They were leaders in integrating microprocessors into refrigerators. I also saw their LED-LCD televisions were rated very high in reviews (one of the top three).
I would say build quality on the Nexus is going to be at or very near the top.
Like several others have said, I will wait until I can see both the Nexus and the Razr first hand and then decide. Also, if you wait a few weeks the price usually drops.