24-120 is known to be a soft lens.. at 24mm @ f3.5 -5.6 it is generally soft.. color wise.. i much prefer the 24-120's colour.. find it a little more contrasty.. well distortion at 18-24 is definitely there.. but i guess it is acceptable.. comparing the 24-120 and 18-70 is not really comparing apple to apple.. a closer comparison would be the 18-35..