Oh no, let's not start the WRX vs STI debate in yet another thread.
I think the point is that they feel different when driven, and the OP should not use driving a modded WRX as his basis to buy an STI after complaining about its power.
That said, it looks like the OP plans on modding anyhow. But even modded to the same levels the cars feel different at WOT due to the gearing and such.