> Svg is also often much larger than a font file, especially one that's subset.

Subsetting is where SVG shines, though.

For icon fonts, you can much more easily subset SVG icons than a font file. Font file subsetting needs dedicated tools like font editors (with Icomoon being a common choice these days) and often manual maintenance/upkeep, whereas SVG tree shaking is a natural part of any web bundler (webpack, etc) and automatically adapts to your icon usage and tools in your web bundler such as bundle splitting/lazy loading.

The Fort Awesome JS libraries behind Font Awesome's SVG icon fonts reduce things further from SVG XML files to tree-shakeable ESM files [EcmaScript Modules] that include just a few pieces of metadata and the lone important path text (sticking to a single SVG path per icon), then build the SVG DOM at runtime (as VDOM in the case of the React library), including making sure it follows fill: currentColor to pick up the text color. Minified and tree-shaken by most web bundlers the ESM files are very competitive with any other font format and the convenience wins of automatic subsetting by web bundler are hard to match.

I was manly talking about icons, but not logos. Icons usually only have one color—which is often the same color as the surrounding font color. If your icon is only a single <path> (most good icons are) then you can color them with:

    svg { fill: currentColor; }
    .parent { color: var(--text-color); }

When you use dark-mode the color of the svg path should change with the text as long as the author changes --text-color in a dark-mode media query.

    @media (prefers-color-scheme: dark) {
        --text-color: wheat;
    }

I don’t know about the size, but I suspect that if any the difference is negligible. Most of my icons are a few hundred bytes uncompressed. And I usually put them in a sprite which is usually well under 50 KiB uncompressed. I don’t know how large font icon files are, but I suspect they are not that much smaller that it makes a difference.

> I don't expect logos in the text to fade into the background.

You can use @media (prefers-color-scheme: dark) { ... } in the style inside the .svg and browsers render it accordingly in dark/light mode. But yes, not being able to set the color from the page CSS is annoying.