I get the feeling that MathML will win out, simply because Firefox supported from early on [1], there is first move advantage. I use an old JS library for backwards compatibility [2] that adds just enough support for any math I'm math'in [3]. I would still prefer SVG, but it ended up being a pain to implement reliably.

One thing I noticed about this site though is that it is laggy - and I have a pretty good system.

[1] https://caniuse.com/mathml

[2] https://coffeespace.org.uk/projects/mathml-render.html

[3] https://github.com/pshihn/math-ml