I had the opposite experience a few years ago, where SMIL performed better than CSS animation but it likely varies depending on what is animated. Problem was on

I had the opposite experience a few years ago, where SMIL performed better than CSS animation but it likely varies depending on what is animated. Problem was only that certain browsers at the time (old Edge for ex.) didn't support it. Thankfully Chromium and FF continue to support it. It has its place and also has supported features CSS has only fairly recently begun to see equivalents for (eg: motion paths).