I have 3 BK Tele bridge pickups, Piledriver, Brown Sugar and flat pole Blackguard. I also have a couple of other Teles to compare them with too. If I tell you that the tone I had on the amp (Marshall Silver Jubilee with 2 Celestion Sidewinders), was set to give the exact ring for the Brown Sugar opening chords, and that the Brown Sugar really had it nailed, I can compare the Blackguard and Piledriver with that.
The Blackguard was jsut as capable of the Brown Sugar sound, however it has a bit more air to the tone and is not quite as powerful as the Brown Sugar itself. It is a very classic tele tone and sounds great for blues as much as when you drive it for rock. It has the sweetest clean tones of the 3 pickups.
The Piledriver will get the tone of the ending to Stairway (as she walks on down the road......). It is a darker tone than the BS and BG, with more power. It can still deliver head cutting cleans, but there is not quite the same top end.
Overall the BG is very versatile, but if you want the darker Broadcaster sound then the Piledriver has it. If on the other hand you love the sound of the Stones, then get the Brown Sugar!
You can see the teles with a bit more description in the Guitars, Amps and Effects section.