I've driven both and had a hard time deciding between the MSP and the Spec V. A drag race or even an autocross type would be very close given equal drivers. The suspension in the MSP is a little more user friendly and secure feeling, but the Spec V will put up very fast times in a slalom and high skidpad numbers even though its a little less predictable at the limit. It likes to lift a rear tire in hard cornering. GTI's also do this. Its a little unsettling, but the Spec hangs on.
Both cars put out some pretty bad torque steer, the Spec V maybe a hair worse. The Spec V produces more low RPM torque. Both have LSD's and the same size rubber.
The Spec V costs a little less in base trim (no ABS) and is also available with options like cruise, sunroof and a nice Brembo brake package that the MSP does not offer.
The MSP looks nicer (most folks think) and has a better interior (most folks think). The N/A engine on the Spec V should prove to be more reliable over the long term as its 2.4 litres doesn't work as hard to put out what the MSP's 2.0 does, especially with the added heat and stress of the turbo bolted onto it.
Its a toss up. In the end, I went with the looks and extra refinement of the MSP. I don't regret not getting the Spec V.