KaTeX weighs about the same if you do care about those metrics, however.

In case anyone wants to look at actual numbers about how much KaTeX weighs for a simple mathematics page: https://news.ycombinator.com/item?id=44614133

Quoting the relevant part from that link:

  katex.min.css              23.6 kB
  katex.min.js              277.0 kB
  auto-render.min.js          3.7 kB
  KaTeX_Main-Regular.woff2   26.5 kB
  KaTeX_Main-Italic.woff2    16.7 kB
  ----------------------------------
  Total Additional          347.5 kB