What benefits do they have over normal sti gearboxes?

Have heard that they have group n boxes but also that they just have dccd

 

Yes mate, Group n short ratio gear box, max speed of about 135, cruses at about 65-70, 0-60 in 4 and a bit seconds, which isnt shy.
DCCD progresivly locks the diffs, 0- diff free for dry tarmac, 1- 15% locked for wet tarmac, and the others are for sand, gravel, snow and ice rallying.

Dale.