Brushless motors have alot of advantages over their brushed counterparts.

1. Lighter weight
2. More efficient.
3. Higher RPM's
4. Smaller size.
5. Less heat
6. Less friction

This being said, the Blade heli doesnt need a brushless motor to perform great. The 9 tooth pinion on the "aerobatic enhancement kit" upgrade is adaquate for aerobatics.

You can upgrade the Blade to a brushless motor, but it requires more than just a new motor. The avionics have to be converted over to use brushless motors.

Brushless motors require a brushless speed controller to work. The standard black box controller in the blade does not have a brushless controller in it, so a conversion is necessary. This requires bypassing of the ESC circuitry in the stock box, and installation of brushless speed controllers. Its a lot of work, but not impossible if your so inclined.