sonos vs airplay

I have a whole house home stereo system, there are hard wired speakers in most rooms. i am looking to add either an airplay system or sonos. my music is all in iTunes and I enjoy Pandora.

1) airport express hooked up to stereo, apple tv, and zeppelin air

2) sonos connect hooked up to stereo and play 3

what are the differences and which would you choose?