Overall, ESBuild feels like a much lower-level tool than Vite. It's great for smaller projects or projects that require absolute and complete control over their builds, but it takes more time to setup in most cases and often requires writing your own build scripts.

2. Compared to React yes, because Svelte ships no runtime (or at least a very minimal one). There is a curve though, and very large apps (in the hundreds of components) will eventually be overtaken by something like Preact or vue.

3. No runtime means no restrictions on what they include in the framework. They take full advantage of Svelte being a compiler and include things like complex state management in the form of stores, a built-in transition/animation system with support for springs. Also the included syntax is extremely concise, if you're familliar with vue it'll be fairly easy to pick up.