> Airplay doesn't offer multi-room audio; AirPlay 2 does
> AirPlay lets you stream from any Apple device to your speakers or TV
> AirPlay 2 lets you play from speakers over Wi-Fi, and it'll stay in sync
> AirPlay 2 lets play different songs in different rooms with multiple HomePods
Personally I've been very happy using AirPlay 2 with recent iPhones, a collection of HomePod Minis, an AppleTV and Denon Receiver. It makes it pretty easy to set up complex audio routing configurations from your phone. You can send a stream to several devices simultaneously while controlling volume independently and as a group. You can see what's playing on each device. Audio quality is good, battery impact seems fine.
I wish I could have strong AirPlay 2 support from non-Apple devices, but I know how the ecosystem works. Still, easy enough to use something like the Emby iOS app [1] to bridge arbitrary content into the system.
> Airplay doesn't offer multi-room audio; AirPlay 2 does
That seems strange. Because I remember buying several used Airport Express base station to build a multi-room audio system. It worked great. That was around 2006/7, if my memory serves me right. At that time the protocol and the feature was called AirTunes.
Doesn't the original AirPlay have a constant 2 second lag? Like pressing Pause will take 2 seconds to take effect. I remember hearing it was something addressed in AirPlay2.
Original AirPlay does have a built in lag, but commands like pause were sent immediately (and if the target has hardware volume control, volume would be instant to rather than modifying the lagged audio stream)
In addition to the features given by others, I believe AirPlay 2 significantly re-worked the way timing and sync works.
Previously I believe AirPlay (1) had a fixed 2 second delay, which was not a great UX and also caused issues in syncing multi-room (or multi-output) audio.
AirPlay 2 does this in a much more dynamic way that reduces the latency (anecdotally, maybe 100-200ms is typical) and improves the sync. I have no idea how it achieves this though.
AirTunes already had multi-room support. It might have been technically different. But you could select to mulitple AirPort Express at once and they would play the audio synchronized.
