I won't call myself an M14 Guru (I really ought to start shooting mine, though the lack of surplus 7.62 doesn't help). I do however have both rifles to compare.
If some dealers still have the Norc M14, I presume that they'll be more than $399 like they were selling for direct from Marstar. The $529 Polytechs come with a well designed synthetic stock, compared to the soft wood of the Norcs that most people replace. So if the Norc costs much over $450, just the stock issue alone will make the Polytech a better deal.
For those of us who want to use the iron sights, it sounds as though getting irons that hold zero are less of a hit or miss proposition (pun intended) with the Polytechs, but the indexing of both Norcs and Poly's continues to be an issue for those wanting to use the sights. I think I'll still have to defer to people who've held more than one Polytech to confirm whether the sights are consistently better than the Norcs, though that's what I've been hearing and reading thusfar.
Cheers,
Frank