It's the difference between night and day. Frankly, the Aveo is one of the worst cars on the road. As the other poster mentioned, it's essentially a Daewoo...not a good thing. Here's what Consumer Reports says about both cars, I'd highly advise going to your local library and checking the magazine out for free. You will thank me.
Honda Fit...
This small four-door hatchback offers easy access and very good visibility, and has an amazing amount of interior room. While not overly powerful, the Fit feels responsive, with a smooth and willing engine, and agile handling. Fuel economy is an excellent 33 mpg overall for the manual and 30 mpg for the automatic. The ride is a bit choppy but supple enough. The Fit comes well equipped with antilock brakes and curtain air bags. The 2009 redesign offers stability control, but only with the optional navigation system. A simpler way to fold the rear seat and a tilt and telescoping
Chevy Aveo...
Other than a tight turning radius, the chintzy Daewoo-produced Aveo doesn't offer much. The engine delivers slow acceleration and returns just 26 mpg overall, which isn't impressive for such a small car. Handling lacks agility, with imprecise steering and lots of body lean. The ride is jittery and noise is constant. Access is relatively easy, but the interior fit and finish is insubstantial and the seats are uncomfortable. The hatchback adds versatility, but the sedan has a roomier trunk. ESC and curtain air bags are not available. Reliability is below average.
In addition, the Fit is the highest rated subcompact car(68/100), while the Aveo is DEAD LAST(36/100). The Fit has excellent predicted reliability, and the Aveo has below average.