definetly, a speed6 weights like 4-500lbs more than a speed3 so what you will make up in sweeter launching car, you will lose with extra weigth and drivetrain loss at speed on the highway.
Even a wrx has a more mod friendly engine and aftermarket set up. An sti or evo will be similar and definitely more fun in the snow and faster than a speed6
My speed 6 destroys lightly modded evo's and sti's. And I can do it with seat warmers, good sound, comfy seats, no noise. I almost got an evo 8 which I sometimes regret but I can tell you one thing. They are not comfortable. You feel every bump, outside noise, hard seats, . . . very plain. You get in the speed 6 and you are like wow . . . this is a nice little setup. Get into an evo and your like . . . wtf is this a chevy cobalt? The new exo X's are nicer on the inside but look like crap on the outside /:. Both cars have their pro's and cons.