The Mitsu has fewer typical problems, such as Subaru and their habitually exploding center diffs and third gears. As far as the Evo having too much turbo lag, that's sheerly opinion. And you're right, in such a case, a BOV will help it greatly. Either way, I hope you have experience with a turbo car, as they are a whole different animal. Lots of new stuff to learn in order to keep 'er on the road. And for the record, if you get a BOV, for the love of Bob, get a ****ing recirculated. The BOV noise is played out, and get all kinds of gunk in the intake tract.
As fat as the Suby goes, with it's shorter warranty, and typical problems, it does have a boxer engine. It's got a MUCH better sound, and smoother accel. It's also going to build torque in a far superior manner. Out of the box, the previous gens performed about the same. The Evo's AWD system receives a LOT of acclaim, because it's Mitsubishi. They talk about how great it is, but they fail to mention that they're using the Eclipse GSX and other brands as a comparo. The Suby AWD system is considered by most, to be better. If you want a good straight line car, just grab a used SRT-4. That's a whole different can of worms, but they are awesome cars, and the World 2.4 is a rock solid engine, when it's taken care of properly, which you should do anyways.
Personally, I'd drive them both, see which one you like better, and take the price stand point from there. You're probably going to be happy with both cars, but if you don't try them both, then always have that suspicion that the other one was better.