I have a pair of the older QC15's (bought about 6 months ago). The only difference I can see is the use of a new "audio" cord that comes with the headphones for use with an apple product. This new cord has a microphone embedded in the cord. Other than that, that's about the only difference I know of. I inquired about this new cord for my set of QC15's but BOSE customer service wanted to charge me $29.95 plus shipping for it. I told him to keep it as I had already paid way more than too much for these headphones.
You would have to purchase a separate mobile communications kit through Bose's website. The kit will allow you to take calls while listening to the headphones.
Here's a link: http://www.bose.com/controller?url=/shop_online/headphones/noise_cancelling_headphones/accessories/qc2_commkit_acc.jsp
I bought a pair for my daughter when she started college. She tells me she couldn't ever steady in her room without them. She also said she would buy another pair herself if something happened to them. I can't speak to the quality of the audio.
Short version: Beats for looks and some additional functions, bose for noise cancelling.
QC15 is smaller than a Studio
-Beats fold in to save space while Bose folds flat
Unless you're not fashion-concious, you'd agree that beats looks way cooler
-you won't be mistaken for someone who just stepped out of a recording studio with the beats
On average, the same, but the bose cancels certain noise that the beats doesn't
-again, usually there's no difference... unless you change environment often.
Bose feels solid and Beats feels plasticy and flimsy
-You can treat the bose horribly, like tossing it into your filled up backpack without putting it in the case and it'll still be safe, although I don't recommend that.
-Beats are prone to snapping at the headband
-Beats comes with free communication cable(mic only) whereas you'd have to buy them separately for the bose, but still somewhat pointless because you have to take your phone out of the pocket to answer anyway. Great for video calling though
-Beats also has a mute button, which well, mutes the music but not pauses it. Great if you need to have a break from music without taking off your headphones but you'll seem rude if you talk to someone with your headphones on.
-Bose's cable is a little too long if you ask me, while beats has a cool, thick and red tangle-free cable
-I'm not an audio expert and to be honest, they sound the same unless your music belongs to the genre they were designed for, i.e. acoustic music for bose and hip-hop,rap and all that for beats, then definitely one will have an edge over the other.