This is a marketing judgment question. Flights from LAX to DEN are $$20$ less expensive than flights from ONT to DEN. Driving traffic is worse getting to LAX than it is getting to ONT. Flights out of and into LAX are generally more delayed than those out of and into ONT. For which reason below do you think most Los Angeles travelers would elect to fly to DEN from either LAX or ONT:

From LAX to save $$20$

From ONT for convenience and to save time