I try to stick to what I know, and since I've never played EMG's, I'll stick to talking about the general difference between active and passive pickups.

A passive pickup turns the vibration of the strings into an AC current that an amplifier can boost enough to drive the speakers.

An active pickup uses the same basic pricnciple as a passive pickup, but there is also a preamp built into the guitar.

This allows better EQ control at the guitar. The preamp can actually boost selected frequencies, while passive controls can only attenuate them. And because the signal is made strong right at the guitar, there is less chance for unwanted noise to interfere with the signal before it reaches your amp.

There are a lot of differing opinions on whether active pickups actualy sound better. Thats something you're going to have to decide for yourself.