Sonos vs. airport express

What is the big diff between these two products: sonos ZP90 and the airport express? Aside from the fact that the sonos will transport the digital audio via coax, and the airport is limited to optical? I would be using an external DAC, so the internal D to A conversion of either unit is moot. Neither one stores media locally, both are meant to receive audio streaming from a laptop or desktop, can anyone shed some light? Thanks!
Rbstehno's right. And:

- vastly superior dedicated remote for Sonos
- marginally worse desktop software for Sonos
- much better multi-zone support with Sonos
- ultimately, no need for a computer to administer Sonos
- actual human being tech support available for Sonos
- one's a weird little box, the other's a wall wart
- some upgrade paths (Cullen, etc) available for Sonos

Depending on your configuration and need, none or all of these may matter to you.

I've had both, and Sonos feels like a $ignificant step up in my household. YMMV.
it depends on what you have and what you want to do. if you already have a mac with itunes on it, and you want to distribute music to 1 or many rooms at the same time, and you have a touch or iphone, you don't need a sonos. if you want multisource capability for music and for audio if you own a pc or mac, then go for an apple tv. IMO, the user interface from the touch/iphone with the latest i tunes is very good. if you need more than that, there are products like airfoil that allow you to transmit xm/sirius over itunes. instead of the sonos devices with the amp built in, i just use a little jolida integrated amp in that room with the capability to change tubes and get the power i need. for a sweet little setup for the price of a sonos, get a music hall 25.2 dac, jolida 1301 integrated amp and use your mac/pc with a touch or iphone.
I would prefer the Jolida 1501 RC, and I need pre-outs or A/B speakers because I run a 2.1 system (B&W 685s and HSU VTF-1). I suppose I can use stackable banana clips on Jolida's single channel, but when the amp clips, if the integrated had pre-outs, the sub would still get a clean signal. Not sure when the 100w Jolida would clip the signal, but...
I currently run AIFF in iTunes on a 5 year old Vaio, for iPod use only. I am only concerned about one room, my listening room. I don't want to buy a new music server laptop, I don't want to buy an iPhone or iTouch. Airport Express seems to be the most affordable way to get lossless PC Audio into my stereo system, and I don't think I am losing anything, even though it is only $99.
Not sure the Apple TV makes sense because this use is audio only, plus I would need a keyboard, mouse and monitor, and space is limited on my desk. The Vaio would be the second laptop on the surface, the other being my work laptop. I know I can store the music on that unit, but I can get more storage for less $$$ in an external drive.
you don't need a keyboard and mouse for an apple tv. you get a little remote with it. for a 1 zone audio only setup, an airport express is all you need. the apple tv gives you the option to stream audio and video plus gives you the option the setup multiple zones all playing different music.
i have a 1301 in my den and a jolida 1701 in my family room. they are both nice amps. i use classe for my audio room.