I just have a commercial OS and a prov BS (both 40deg) on similar blades, the BS on ZQ S-ALC 90 and the commercial H3N on the ALC side of an Ice Cream. Both are boosted and honestly the difference exists but not that much.
I have more hours in the commercial OS H3 so the sponge is broken in well already I think, while the BS not yet.
OS seems to be faster until I start to hit very very hard or step back. OS has higher arc too.
BS has more stable control and more linear across every shot type. Open up, 3rd ball kill, push, block, counter, smash high ball etc...
At this moment I think I still like the OS better, beacause it's quite bouncy in fact and the higher arc it produces makes it easier for me to pick up some balls where I am late / far back against short pips players. Just more relaxing to play with the OS.
However because of the higher arc and more bounce, and possibly a bit softer too, countering over the table and sometimes blocking is a bit unpredictable andit is a bit sensitive to incoming spin.
I think the main benefits of the BS is easier boosting, lighter, more stable / linear control, the arc of the BS is more sharp and for sure more uncomfortable for the opponent. BS is just more stable at countering in all distances.
Actually I am a bit interested to put the OS on a Mizutani SZLC since that blade has a bit of a kick compared to a Viscaria like blade so it might fix the lack of umph if one steps back with OS. And the "passive" bounce of the MJ SZLC is not that different (possibly even less) than the previously mentioned blades.
These all might sound like pretty signigicant differences, but not really, they are very similar. So if someone doesn't want to shill out the double money for BS provincial then a commercial OS is more the fine. Just buy Seamoon and boost the OS a bit more than BS. Seamoon is much cheaper than how much extra a BS prov is compared to plain old H3N. And while I have a pretty positive experience with BS durability a lot say it can bubble up much earlier than OS so there's that extra cost too.