That car will literally last forever. I'd go for the lower mileage one, but you're not going to go wrong with either.

What to look for? First of all, run the VINs through Carfax just to make sure they weren't fleet vehicles, or wrecked, or had the mileage rolled. Check the tires and see if they match and have even wear. Look under the hood, in the trunk, in the wheel wells, and in the door jambs for overspray for repairs or other indications that it might have been in an accident. Of course test drive it. It should track straight, not have any rattles (or any bad ones), and should be a lot more ballsy/fun than your Sunfire. If anything seems out of place or odd, ask a question about it. Here's a start: ask the owner of the white car when the battery was changed. It is obviously an aftermarket (AC Delco) unit.