Comment by PantaloonFlames

I recently had the occasion to work with a client that was heavily invested in XML processing for a set of integrations. They’re migrating / modernizing but they’re so heavily invested in XSL that they don’t want to migrate away from it. So I conducted some perf tests and, the performance I found for xslt in .NET (“core”) was slightly to significantly better than the performance of Java (current) and Saxon. But they were both fast.

In the early days the xsl was all interpreted. And was slow. From ~2004 or so, all the xslt engines came to be jit compiled. XSL benchmarks used to be a thing, but rapidly declined in value from then onward because the perf differences just stopped mattering.