Stock for stock, there won't be huge differences between your EVO and the MS3. If anything, the MS3 may "feel" faster because of its FWD nature, it's sort of chaotic, but that's also the fun factor
. Also, because it's only driving two wheels, there's less drivetrain lost.
Won't comment much on the styling because that's highly subjective. But I love the way it looks, I think its sleeper look is quite stylish.
If you can convince yourself you'll be happy with ~300-350hp and can care less about AWD, get the MS3. It's cheaper, more practical, more or less equally fast from factory.
But if you think you won't be satisfied until you hit 400hp, and you feel like you can't live without AWD, keep the EVO or look elsewhere. I won't ever get near 400hp with my MS3, so please don't quote me. But I think it'll take more work to get 400hp out of the MS3 than it is for the EVO.