The perf blogpost actually uses SpiderMonkey-compiled-to-Wasm as a benchmark rather than a comparison (peer) of Wasmtime. However, there are some good comparisons done by a third party in this paper:

https://arxiv.org/pdf/2011.13127.pdf

See Figs. 20-22 on page 19. They found Wasmtime to be quite competitive to V8 and others.

(disclosure: I work on Wasmtime + Cranelift)