[Radio Wrangler]

I suspect that not all the range of goodness/badness is a direct effect of the transistor's gain. With the simple bias arrangements used, the change in gain will move the collector voltage around some will be close to saturation, some close to cut-off and some may be around the middle.

Playing about with the base resistor value could extend the range of transistors which are reckoned to produce good results. The yield could be better than just blindly swapping transistors. Doing the same with a 'god' transistor and looking at the collector voltage would shed light on whether the best sounding pedals are nearer cutoff or nearer saturation.

David