What specifically is better? These are just clients for the Streaming that Steam provides, right? They don’t actually swap out the “server” side, right?
They’re completely different implementations of systems that steam video/audio/inputs.
Valve’s is pretty buggy but has deep integration with Steam and allow NAT traversal, while Sunshine/Moonlight are way more reliable, have features that reduce latency but are pretty barebones as far as features: they just do streaming with no tight integration with what’s being streamed.
And Sunshine is a reverse engineered version of Nvidia’s game stream server, since Nvidia sunset Gamestream a few months ago.