The power does not matter. BUT - remember one click equals one fourth inch movement ONLY at 100 yards. When you go another 100 yards, or to 200, it doubles, or one click equals a half inch. At 300 yards, one click equals 3/4" at 400 yards, one click equals 1", and so on.
They all are but it's best to sight in on your highest power.
Really, why? My standard has been to sight it in with the magnification you will most likely use in the field.....just in case it moves anything it's not supposed to when you dial the power up or down.