All these 3 models have different turbo and power. WRX (220HP), STI and spec c (280HP). Spec C is the "diet" version of STI which is much more lighter body, better suspension setup, handling and torque.
Turbo
(Based on MY03/MY04)
WRX = MI Spec 220HP ( TD04 )
WRX = JDM Spec 250HP ( VF22 )
STI = MI Spec 265HP (VF34)
STI = JDM Spec 280HP (VF37) Twin Scroll
STI Spec C only produce for JDM = (VF36) Twin Scroll
STI Spec Type RA (RACE ALTERED SPEC) = Limited edition (only 400 produced), The most aggresive spec in STI family (VF36) Twin Scroll
S201 = Special edition for GC
S202 = Special edition for bugeye
S203 = Special edition for blobeye
S204 = Special edition for Version9
STI V-Limited (555 produced)
STI spec C V-Limited
*Only spec C, s202 and Prodrive spec does come with the roof vent. The vent can be open from inside of the car.
*STI does have a lot of sub-version models.