A:
I bought the HK Onyx Studio Portable Bluetooth (Deal-of-the-Day - $149) and the Bose SoundLinkIII to compare the speakers. I kept the HK because of the quality of the sound. I had read many reviews about both speakers and talked to BB staff. The HK had a noticeably richer sound than the Bose SLIII, especially in a moderate-size family room with four walls. The difference was especially noticeable with vocal and instrumental. The quality difference was less noticeable in a large open room. I had listened to the Bose SL III and the SL Mini in the store and thought that the III was better than the Mini.
The Sonos uses wi-fi and I wanted a bluetooth speaker. I tried the Sonos in the store and it does have a good sound.
I learned that it is important to try the speakers in your own home, with your own music, and your own usage (portability, battery, etc.) I have a Sony SRS-X3 ($100) that I originally bought and it fits my needs for portability and price. I had not considered the HK until I saw it on sale and after listening to it, I am glad that I purchased it. The SL Mini might have been a good choice if I was only going to buy one speaker. I had intended to only buy one speaker when I bought the Sony, but the HK price was tempting and I really liked the sound. I now have two speakers that meet different needs.