My vote is near the turbo. I doubt there's a significant difference with wherever you'd put it, but here's my reasoning:

What is the point of a BOV? To vent pressure before it goes through the turbo and tears it up. What I envision happening is a pressure wave being created at the TB when its slammed shut, and working its way back to the turbo. I would think that by the time the BOV is open, this wave should be near the turbo and ready to exit out the now wide open BOV.

Again, I don't think any placement is wrong, and I would be concerned with packaging and maintenence concerns before theoretical airflow dynamics come into play. Plus I'm just a dumb guy running 17 lbs with no BOV and enough compressor surge to give you a hard on