One of the major reasons that I suggest the ziess is that I live in northern Alberta and in November our days are very short.As such you want the brightest scope possible to make sure that you have no problems shooting during all legal hours.I used to have leupolds on all of my rifles but I did miss out on a couple of opportunities at last light with deer on the edge of cover because I couldn't place the crosshairs properly to ensure a clean kill.The slightly brighter ziess and swarovski scopes provide extra insurance against any such future problems.
If you were to usea $50 scope as some would suggest you would lose the best half hour of the hunting day ,namely the first and last 15 minutes of the day,because these cheap scopes are not bright enough in low light conditions..