Six of one, half dozen of the other. Doesn't matter, especially now that both configurations are available, pick what suites ya.
I already own a Shield 40, and had a 9 on the way when I saw the new NS models would be available. I will probably try to trade/sell them to get NS models, so they are like all my other M&P pistols. But it won't be a priority unless I decide to use them for concealed carry, then would much prefer the NS Shield models.