With only 20-ish milliseconds to load, parse, and execute, the size difference disappears into the noise and is irrelevant. In addition, that difference definitely does NOT scale. As you add more components, the ration of component to framework becomes larger and larger as the internal wiring is used over and over again. All those things in the framework have to be re-created quite often in svelte. Even if Svelte could fit all its component changes into the same area as a React-style component (which I doubt), that extra 9 or 21kb would still disappear into irrelevance.