What does the blue book say for each car (to give you a relative idea of price for both)?

What are the option differences between the two cars?

How well have each been followed in terms of maintenance and proactive (change transmission fluid and other items)?

Color - do you like one vs. the other? A perfect car with pink exterior might perhaps not be someone's first choice

An '01 has some advantages (simpler driveline) vs. an '04 (iDrive with solenoid system).