I have driven and worked on both the Cruze and Sonic in the past week. The Sonic, what I like is the head lights. Thats about it. The rear tail lights are way too big for the proportions of the vehicle and the gauge cluster looks retarded. I drove the 1.8 and you have to beat the shit out of the engine for it to do anything, even then it does not.
The Cruze however is better in pretty much every aspect except in the headlight department. Much better interior. I drove the Cruze in the 1.4 turbo trim and the engine is fantastic. I would say it is reasonably quick. And in RS trim it looks pretty damn good.
Now I know you can get the Sonic with the 1.4 turbo, but I would not have it over a 1.4 turbo Cruze.
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1989 Mitsu Mirage Turbo Hatch, 4G63T swap and more goodies to make it a low 12 sec car.
Better to own a Volvo, than be owned by one.
I work for Buick....... and it's not nearly as fun as it sounds.