I use the digital optical to feed a PS Audio DLIII DAC. This feeds a Denon 4311CI receiver. Since it is analog, I can use the Denon to feed the signal to zone 2. There are limits to what can be done with HDMI in different zones.
I use HDMI for anything with video.
The reason simultaneous is important is because I don't have to mess with the ATV's settings when I want to switch from optical to HDMI. The mini requires a setting change, which can be a pain.
Ahhh, not bad.. I guess AirPlay in this situation must be nice to feed audio to a second zone.