3-9 x 40 vs. 3-9 x 50

[Lloyd Smale]

Only thing i see it adds is a bit of light gathering if you insist on buying a cheap scope. A good scope with good glass will pick up all the light you can use with a 40mm objective. Field of view is related to eye relief but not to objective size. if your comparing two scopes that are identical other then objective size and the 50mm one is noticealby better in low light then the 40mm you basicaly have a scope with pour optics.