I thought the NEUs were HDs? Maybe not?
My Swaro SLC 15x56s are definitely the HDs, and they are fantastic.
I would go 15x56 SLC HD over 12x50 NL Pure as long as you have a good set of 10x42s also. To me, the 15s are a bit much for glassing under a mile. I like a wider FOV for that distance.
I have hunted with guys who only have the 12x50 NL Pures, and a buddy and I with the 15x56 HDs were able to pick out pronghorn at 4+ miles and tell the difference between does, an average buck, and a good buck from that distance. Not necessarily HOW good, but definitely could pick out the bigger bucks from the smaller ones to see if they were worth a closer look. The 12s could barely make out the difference between the bucks and does.
If you only have one set, the 12s make a bit more sense. Sure wish Swaro would release an NL Pure 15x56.