Just coming from a Steiner nut, and having a pair of the 7x56 NightHunters, I can shed some light on your question. The NightHunters are the top of the line poro prism bino's that Steiner makes. They use the best glass and broadband coatings that Steiner has to offer. They also carry a 30 year warranty as opposed to a 10 year warranty on the 7x50 Marine. The 7x50 bino's utilize magnesium fluorite coatings on the Marine's. The NightHunter's utilize the companies best glass and High Definition lens coatings which is held company confidential. Also, the NightHunters utilize an internal baffling system to maximize light transmission and minimize stray light. What this all comes down to is that the NightHunter's are the brightest and most accurate color representation bino's available from Steiner, with the possibility of their new Peregrine's, which I have not spent any time with. If there is a brighter binocular out there than the NightHunters, I haven't seen them.
P.S. I have a pair of 7x50 Military/Marines and the NightHunters are much brighter and more accurate. The 7x50 Marines are not the same quality as the Military/Marines. I believe the 7x50 Military/Marines are their most popular selling poro prism bino's. I own several pair of Steiners and my new favorites are the 8x42 Predator roof prisms. Hope this helps you. Chris is a very busy man,so I just thought I would through in my 2 cents worth.
Edited by Roy Finn