I am not sure if either fast or convenient applies here. Maybe I have different definitions.
I think they mention fast because the built-in Deno webserver is now faster than node:http. I've been following Deno for a while, and even deployed a service with it, and it's awesome that it has finally surpassed node performance.
I think if you've used Deno before convenient definitely fits, you can build quite a bit without needing external libraries, typescript by default, you kinda just start working on your problem - just a much cleaner version of what node could have been in my experience.
Just use uWebSockets.js[1] in node, and you'll leave Deno in the dust again. (uws is also what's under the hood in bun)