To be honest, according to Consumer Reports, Pontiac and Chevy's usually suck. Like really suck as far as reliability and exterior/body integrity, safety rating, mpg...etc. If you are looking for reliabality and a car that will last you to 200,000 miles easily with great MPG and safety ratings go with a honda or toyota. they are out of most kids' budget, but they are good cars.
Oh, and if you are buying used (which I am assuming, 2006) go to
www.kbb.com to see what the car is ACTUALLY worth, not just what the dealer wants you to believe it's worth.
But if you insist on a pontiac or chevy, get the cobalt. It gets better mpg and is better quality.