Id definately shy away from the Subaru if you plan on doing any mods. Reason I say this is because usually when you mod a car the dealerships can become real picky on fixing them. Youll normally end up having to do a lot of work yourself and with the Subaru work shop manuals are scarce and VERY expensive. Also parts for the damn things are pretty damn pricey as well.

Id opt for the GS-R. Its a step above the civic in terms of creature comfort and performance. Workshop manuals are inexpensive and easy to obtain and the engine is a piece of cake to work on unlike the flat four of the Subaru. Also parts are more readily available (both hop up and OEM) and less pricey.