gt vs rousch
 

somebody tell me the difference? is it faster?

I'll answer as generic as possible........
 

Depends on what trim level you're talking about.
ROUSH comes in a variety of trims for the GT, V6 and even the Cobra.

Define Perfeormance additions:
>UD pulley kit
>T/A
>Cold Air Intake (CAI)
>Supercharger
>Suspension pkg (varies also but they replace shocks/struts and springs)

Stage 1: body kit {comestic} with options performance/interior additions
Stage 2: body kit and suspension with options performance/interior additions
Stage 3: the whole suite ...S/C, suspension, body kit and interior upgrades

A stock GT can be just as quick as a Stage 2, dependent on the level of performance additions

Hope this helps. :)