Easily Vue 3, the dev tooling/xp + docs are much better over Vue 2.

Vue 3 is more exciting, but I'm stuck on Vue 2 for my real work due to dependencies. Much of Vue 3 has been backported, and you can use Vue 3 like Vue 2, so it doesn't matter too much... probably go for 3 as it's the standard now.

I've looked at Svelte. I was deterred by lack of ecosystem. Vue's is just big enough to be workable, I think Svelte doesn't offer enough to reach the Vue/React size - probably.

Vue 3. Apart from the fact that it is modern and has more features, It uses proxies, so it doesn’t have the vue2’s reactivity gotchas.