I think the difference is noticable if you look next to the rear lights. Also the rear arches seem a little more 'voluptuous' (is that a word?) But i'm sure if you see the car IRL the differences will be more obvious, we all know pictures don't do the 997 justice...
Is the 4s available with the -20mm suspension? The picture of the grey 4s at the start sign makes me think it is...