Well when you drop the throttle and are at full boost (spooled), the engine is taking in less air, and the compressor is still putting out the same amount. Wouldnt it make sense to have the BOV release the pressure as close to the compressor as possible? Or am I thinking of a wastegate? I guess I'm not really sure of the difference in the workings of the two.

To me, I always thought a wastegate opened when there was too much boost ("regulating" the pressure) and still on the throttle, and the BOV was there for when you shifted and the engine suddenly didnt need all that air because the throttle was closed.

... Now that I think about it, cold side would make more sense because it is closer to the throttle butterfly, making it a faster release, and allowing the turbo to stay spooled for when you got back on the gas. I guess I kind of answered my own question there didn't I hehe.