I would buy the cars in this order:
- 4th Gen LS1 (Pontiac) - fast and very drivable on the street.
1st Gen (Pontiac) - One word: Classic
2nd Gen (Pontiac) - a nice '73 SD 8)
3rd Gen (Chevy if its a mid to late 80's, Pontiac if it's newer) - IMHO, the one time Chevy had Pontiac beat in the looks dept.
4th Gen LT1 - Skip it :P