Well I have an 06 WRX and my friend has an 05 SRT-4. We love eachothers cars almost as much as we love our own cars. I love the punch that his car provides when you hit the gas while he loves the fact that I can take a turn unlike his would be able to. It just depends on what you like. The best thing you can do is test drive. Mod for mod you won't beat the SRT-4. Stock that car puts down roughly 30hp more than the 06+ WRX. Bolt on mods are also much more responsive compared to the WRX. For the WRX you will want to get some kind of EM like the Cobb AP. Stage 1 is good and stage 2 is even better. With the SRT the stage 1 kit is good; add a turbo back exhuast and the car screams.
As far as a straight line we did line up. Stock for stock I got him off the launch and by the end of 90mph he was just starting to pull past me. From a roll he had me by 2 cars by 90mph. Now my stage 1 with spt cbe vs. his car with motor mounts and short throw shifter I take him by 1.5 cars by 90 and he won't pull on me from a roll. Thing is, all he has to do is add one power mod and he'll take me.
Just drive them both and go from there.