Vortex Viper 4x12x40 vs the Nikon Monarch 3x12x42, does anyone have a comparison. The more I look the more confused I seem to be. Does the argon in the Viper better than the nitrogen in the Monarch? Is the 42 mm noticeable over the 40 mm in the Monarch?. Is the eye relief noticeable-Viper I think 3.7 vs 4.0 in the Monarch. The Viper is about 40.00 cheaper. Any real actual knowledge of comparing both?