I have never handled an NEF so I cannot say for sure, but I think that you would be better off buying your son an 870. The 870 express is the benchmark budget shotgun, parts are cheap and easy to source, resale value holds, and they have proven themselves reliable. I don't know what the difference in price is but I would say that you get better value with the 870.
NEF and Remington are both apart of the freedom group company so the quality may be par, but I would still sway 870 for all the aftermarket.
And I don't even own an 870...