Both platforms have run serious enterprise systems reliably for decades, and the choice between them today usually comes down to context your organization already has, more than a technical gap between the two.
Where .NET tends to fit naturally
Organizations already standardized on Microsoft infrastructure — Azure, Active Directory, Microsoft 365 — get a lot of integration value from .NET that isn’t really about the language itself. Modern .NET (Core and beyond) is cross-platform and genuinely competitive on performance, closing the gap that used to exist with the older, Windows-only .NET Framework.
Where Java tends to fit naturally
Java’s ecosystem and tooling for large, long-lived enterprise systems remain extremely mature, with a huge pool of experienced developers and a track record on exactly the kind of large, multi-team, years-long systems enterprises tend to build. Spring Boot in particular has become something close to a default for enterprise API development in Java shops.
What the comparison usually misses
Raw performance differences between the two are smaller today than they were a decade ago, and rarely the deciding factor in practice. What actually decides it: what your existing infrastructure is built on, what skills your current or available team already has, and what the surrounding ecosystem (libraries, internal tools, hiring pool) looks like in your specific industry and region.
The practical takeaway
This is a case where “what do we already have, and what can we hire for” is a more useful question than “which is technically superior” — because for mainstream enterprise application work, both platforms will reliably get the job done.