Auto will change the exposure values (contrast,saturation,color,sharpness and others). Where manual will not.
Shoot the green box and your pictures will be fine but might as well bought a good point and shoot. All the buttons and dials help give you finer control over the image and if set correctly will give you the same results as auto, it is more than just shutter speed and aperture.
A comparison would be Canons 18-55 kit lens and the 17-55 F2.8 lens, at the same F stop, focal length and speed the images are different. It is the other things that come into play.
2000 740i-Annalisa and 2008 335i-Weebl. Weebl may wobble but has DTC
2012 X5d in Sparkling Bronze ( The Ultimate Cat Carrying Machine)