We made a test some time ago and i think it didn't do too much difference (against Maxims), on the sense that it required almost the same number of bursts at almost all distance and cover.
It makes a big difference for AoE suppression, I found it fairly noticeable when facing the AA HT's and .50 cal. Obviously the most meta would be 3 shrek bulletins.
Why do the penetration bulletins exist for the Jadgtiger? I don't think theres a single tank in the game capable of bouncing it...