I have used both Bose and Zulu's. I would strongly recommend the Zulu, it is very comfortable and well priced. The passive noise reduction on the Bose is non existent but in contrast very good on the Zulu, just in case the batteries run flat on you. Along with that, it is said that the Zulu's have marginally better active noise reduction. The Zulu's (like DC's) can handle more of a beating and won't break if you drop them. I never use the MP3 function on my headset and would agree that is a bit of a waste of time but sounds cool.
A word of warning. If you are buying Bose Aviation X's from ebay, make sure that you check that it has the right mic for the aircraft you are operating. There are two different types.