A requirement for 500 hrs on type saves the companies money on training and tr's.
The more important question to ask is total time and experience.
After the Colgan crash last year the U.S authorities were looking to implement a plan of more than 1500 hrs before you can fly a passenger/commercial flights.
Did this happen yet??
Would you feel safer with an fo at the controls on 1500+ or 250+ who had 500 on the type rating they just purchased on the way out of flight school???