I've not perceived any Performance improvements beyond the first page opening, which is probably because that's SSR and then shipped to the client pre-processed. pages usually render within 100ms in both svelte and angular (including the rest call for the data) and there is no stuttering or anything in either unless I implement a leaky feature... Svelte is sometimes even slower, because it needs to fetch the component itself, which is usually prefetched in angular. (Bigger initial payload because of that but that is manageable as well using modules in angular)
And svelte is so much less mature in tooling/hooks etc that I'd expect it to be significantly more tiresome to use in bigger projects.
Its definitely a very interesting framework however. Having the option to choose which component to SSR and which to process fully on the client is incredible.