This is not about IOR in general but specific experience with the 2.5-10x42 vs. the new 35mm 2-12x32 scopes. At a $1000 vs $1200 respectively the 2-12x32 in a sense pays for itself since it comes with a set of rings. I would like to hear any experiences you guys have with either of the scopes particularly the 2-12 version. How does the larger objective in the 30mm vs the smaller objective but larger 35mm main tube affect brightness and light gathering capabilities between the two?