The stock the Yaris pulls better dyno #'s. Its better on fuel in real world use. The aftermarket support is better on the yaris, there are guys out there with 120-130 HP Na motors with bolt ons.
Full exhausts, intake manifold swaps, throttle body swaps, Its been around longer..
Dont get me wrong, I love my M2. and one day I aspire to have 120-130 HP NA and be under 2000 LBS with me in it, its just not as easy in the M2