Starting in 2nd gear makes you less likely to wheelspin on slippery surface.
It must be pretty obvious, if you've tried using the switch, that in 'E' mode the car is very slow, and won't rev over 3000 rpm, and in 'S' mode it is much faster, and will rev to the redline??!
And then you can figure out that in the 'slow' mode (E) you will get much better fuel consumption..
2.5-16v 1990 90,000m Astral Silver
2.0E 8v 1986 107,000m Black