The only difference I know is the apparent field size. The Nagler is 82 degree the Panoptic is 68 degree. That means the field size or circle your lookind at in the eyepiece will be bigger with the 82 degree. I've seen both eyepieces. It's the only 31MM eyepiece with a 82 degree field. And that's all I can say without mentionibg the price. It looked good but for $600 they can keep it. The Panoptic 35mm is a great eyepiece and well worth the money. You can get 2 real nice eyepiece for the price of the Nagler 31mm, even 2 Naglers.
That's it;
BOB SAL