PT Cruiser or 2005 Pontiac G6?

[DanesAreLove]

I'm looking to buy my first car, and so far my dad has found a really good deal on the Pontiac about $5000, for a car with only 6,000 miles! It has been in a car accident, but my dad can fix it up. The thing that worries us is it has 6 cylinders, and gas is so expensive.
Another car we're looking at is PT Cruiser. My dad could get it for cheaper than Pontiac G6, and it has 4 cylinders. But I looked up online and found out that both cars get about 20mpg, so I don't see much difference there.
Another things is I have a 130lb Great Dane that I'm going to be driving around with me :] I heard that Pontiac G6 are spacey in the back. And I really don't like the look of PT Cruisers much.

How do the two cars compare on gas, space one the back seat, and overall quality?

Thanks so much!