Funny thing is, GM already had a Turbocharged 2.0L ecotec available. GM's Saab division uses it. All they had to do was drop it in, but i guess they prefered the supercharger or else they wouldn't go through the trouble of developing one for the Cobalt. Here are the ouputs between the two motors. The hp output is pretty close with the Turbo ecotec putting out 5 horses more, but the tq figures aren't really close...especially when looking at peak figures relative to rpm.
S/c'd ecotec - Cobalt SS - 205hp @ 5,600rpms - 200lb-ft tq @ 4,400rpms
Turbo ecotec - Saab 9-3- 210hp @ 5,500rpms - 221lb-ft tq @ 2,500rpms
Turbo engine makes 21lb-ft more tq at almost 2,000rpms earlier. Pretty tq'y.
Me personally...i prefer S/c'ers on bigger displacement v8's and turbocharger on smaller displacement 4's and 6's.