Great question! I wrote a blog post yesterday going into the nuances of this a bit: https://zaplib.com/docs/blog_ts++.html The short of it is that Rust+Wasm isn't much faster than highly optimized JS in most situations, but it's hard to optimize it. In Rust it's a lot easier to get to the same level of performance as highly optimized JS.

We also support building compiling to native though, and we've found that the typical difference between Wasm and native apps is about 2x (on most metrics).