STR02 and RB03 were very similar in the first 2007 races (like twin sisters) but during the season the 2 cars had more and more differences (especially the front and rear wings) . The new developments appeared firstly in RB03 and then were inherited by STR02 .
It looks as though the wing mirrors supports are Far longer on the RB3, and maybe the rear wing endplates on the SR2 are slightly longer at the bottom.