I went around in circles with this before eventually choosing airplay.
Reasons for my choice
1. It works from iphone, ipad or any Android device (though not as seamlessly on Android in my experience)
2. There are various airplay speakers available.
3. An airport express can be plugged into any amp or set of amplified speakers to get music wherever.
4. An apple TV can also be used but adds video if connected to your TV
5. A raspberry PI running RASBBMC can also airplay sound and video for much less money.
6. With itunes running on a computer you can airplay to multiple sets of speakers (wish apple would add this to iphone airplay)
7. It’s apple so tends to work rather than be a constant hassle.
Cons as I see them are
1. It’s wifi, if you have signal problems it will not work.
2. Hmm, can’t think of anything else right now.