I've finally decided to get a Nightforce NXS 5.5 x 22 for long range shooting. My goal is to shoot past 1500 yards. I'd appreciate some input on which objective size to get. I know the 56mm will let in more light, but other than that, is there a reason to get one? The only draw backs I can think of are that they are heavier and I'd most likely need some kind of cheek piece. The cost is the same. Are there any other benefits and/or disadvantages of getting the 56mm objective over the 50mm??