What is the difference between these 2 types of drivers?
The configuration used to drive a bipolar LED is an H-bridge, where the half-bridges are two push-pull outputs of one or more digital devices. While it is possible to drive a unipolar LED with an H-bridge, there is no benefit to having the voltage reversed on it and so one can save an output by tying the other end of the LED to either VCC or to ground, depending on which terminal is connected to the output.