I built a text annotation tool recently, first in React before rewriting it in Svelte. I found React's virtual DOM annoying, esp. when dealing with text selections + wrapping those selections with elements, etc. Svelte was just simpler in this regard (and overall, IMO).
But if you're not a frontend dev and want to use lots of off-the-shelf components, Svelte's ecosystem is much smaller than React's, so you won't have access to full-featured component libraries like MUI, Chakra, etc. Additionally, Typescript support is stronger in React (it's mostly there in Svelte, but lacking in some areas [1]).
For both React and Svelte I found XState helpful to manage annotator state. It might not be necessary if your app isn't terribly complex (in particular, Svelte's built-in stores can handle complex state well), but I've found it a good way to think about state+events and more confidently make changes as a result.
I think it’s worth nothing that pretty much any vanilla js library works out of the box with svelte with very little extra effort. Don’t discount the size of that ecosystem
But if you're not a frontend dev and want to use lots of off-the-shelf components, Svelte's ecosystem is much smaller than React's, so you won't have access to full-featured component libraries like MUI, Chakra, etc. Additionally, Typescript support is stronger in React (it's mostly there in Svelte, but lacking in some areas [1]).
For both React and Svelte I found XState helpful to manage annotator state. It might not be necessary if your app isn't terribly complex (in particular, Svelte's built-in stores can handle complex state well), but I've found it a good way to think about state+events and more confidently make changes as a result.
1 - https://github.com/sveltejs/svelte/issues/4701