Impossible to say..

Std Evo 6 = around 270bhp
Stage 3 cossie = Anything from 250 - 350bhp (I've seen them all ) and equal variations of torque.

Esc Cos is lighter (especially if it's not the full blown late version safety model)
Cossie has more transmission losses

This is all straight line stuff anyway..

I would say Cossie IF it's a decent stage 3 and running right. Not sure sure if there was a corner involved though.