The article mentions that Ava differs from Jest because of its focus on speed. Just figured I'd mention we are in the process of migrating from Ava to Jest, and we gained a 5x speedup in running our entire suite.
Jest improved so much since its first release, in the beginning it was mentioned only to test React components. Ava made the speed its first selling argument but Jest may be even faster, now... Thank you for your remark, we are going to update the comments accordingly, to say only "AVA emphasises on speed", removing "Compared to Jest".
I never understood the Ava speed claim. Always was much slower than either Mocha or Jest.
I don't know for sure, but I think Ava embraced testing concurrently before the other testing frameworks did.