Would highly suggest listening to the "How I built This" podcast[1] with the peleton founder John Foley, really great story with usual tech themes like doing things that don't scale and finding a niche but loyal customer base and expanding organically.
[disclosure I am a sanic contributor] aiohttp is a great project, very similar to sanic, I'd say the big thing is sanic is slightly more flask like than aiohttp in ergonomics (which is something aiohttp has been working on[1]).
Sanic also makes performance a key development goal so you can feel comfortable the project will scale gracefully. But I will stress I don't have current benchmarks to compare against aiohttp
[1] https://play.google.com/music/m/Dmjr6m5i4h3j6gaysgjd47ryhci?...