Same thing happened to me when my Behr neck snapped. I was told the Nissen was all aluminum but when it arrived the neck was not reinforced. I already had my car down for a week and did not want to wait another week or so for the Behr to arrive so I kept the Nissen.
No problems with the Nissen, no leaks and the fit/finish is ok, I agree that the Behr is a nicer unit. No temp increases either, seems to be the same