AirPlay and optical audio: Apple TV vs. Airport Express

[Puonti]

In my current setup I have a 5.1 speaker system connected directly to my iMac's optical out. There's a wireless network in place, running off a Time Capsule.

With Mountain Lion's ability to stream system sounds directly to AirPlay receivers and my need to re-arrange things in the living room, I'd like to switch to wireless audio. For my situation and needs, am I missing anything in comparing the Apple TV to the Airport Express:

1) Both can receive AirPlay audio just the same (wirelessly or through ethernet)

2) Both have an optical out similar to what my iMac does, so I can connect my speakers with the cable I use now

3) If there's any delay in audio playback (system or iTunes), it's the same on both

4) Obviously only Apple TV can be used to AirPlay video or mirror a desktop

5) Likewise only Airport Express can actually create a wireless network, should my Time Capsule crap out

6) Apple TV requires a TV or projector to set up (I don't have either one right now), while Airport Express doesn't

EDIT:
I should note that the audio cable I use right now is an optical S/PDIF cable with a mini-TOSLINK plug attached to it.

 

[waw74]

if you have a television at the location, i would go with the aTV.
if not, i would go with the express.

you will not get 5.1, unless the file is in iTunes, and you are playing the file on the aTV.

mirroring also will not get you 5.1
also mirroring only works on the newest macs (mid 2011 or newer)

 

[SDAVE]

Both AE and ATV use Apple Lossless to transfer audio over via AirPlay.

However, I can tell that ATV sounds a bit better than my AE...but then again, I do have a fairly old AE (first or second gen I believe). But it is connected via Ethernet to my home network, so not sure why it doesn't sound as good as the ATV.

 

[Puonti]

I had missed that 5.1 limitation over AirPlay, so I'll have to evaluate how big of an issue it is. Thank you both for your input!