This is a really good question, I think you should have a read of this post we made earlier in the year when we made the switch.
We learned the hard way that, for Speckle’s IFC importer, reliability was far more important than raw performance.
Our goal with switching to IfcOpenshell was not to make small-medium sized files import faster, it was to be able to process (at all) larger and larger files reliably.
Going into our new IfcOpenshell based importer, we knew that we would require a more powerful machine in order to match the performance of our older importer.
But once given the right sort computing power, IfcOpenshell is able to efficiently utilize it!
Since that post we’ve found a few more tricks to make our importer even faster and more memory efficient. So any numbers we quoted in that post are no longer accurate.