Thanks for the kind words, and I get where you're coming from... however, this is not a PITA mod that only provides minimal enhancement. It's got a great $$$ (or Euro, or GBP, or Ruble) to smiles ratio. I should have done this a long time ago, even before the exhaust mods. It's that good, and it's fairly cheap (less than $300) and so easy to install.
The BPV versus BOV performance difference would make a good debate. Having seen first hand what happens when a pump overheats due to its fluid being constantly bypassed, I would side with a BOV being the better performer. I have a P3Cars digital vent gauge, so I could measure the difference in IATs when driving around at high rpm, but I'm not too keen to replace the brand new gasket I installed. The difference is probably minimal anyway.
For you, I would recommend the Turbosmart just because it's adjustable. I already knew I wanted a BOV, since I have one car that's silent (Tial QR bypass, non-M Z4), and one that's in the middle (G-Power Z4M).
Here's a rather dull video highlighting exactly why I made the switch from the squeaky bypass to the Tial: