I haven't tried the Sony ones so I can't say much about them. However, I own the M50 and I have to say, they are excellent headphones. They are monitor headphones, meaning they deliver the sound "as-is", without any extra bass or frills. I used to own the ATH-PRO700, which is Audio Technica's "DJ-use" set, and frankly while the bass was amazing, jazz or film scores just didn't sound quite right on them. I realized I wanted a set that was well-balanced, because I listen to a wide variety of music. So, I would say decide by the type of music you want to listen to. If you listen to mostly bass-heavy music, the DJ Sony might be the pair for you.
That being said, the M50 is the best set I have ever purchased, and I cannot recommend it enough. They are comfortable to wear over extended periods of time (which I cannot say for every set I've owned), they sound brilliant, they look great, and the sound leakage is low (not perfect, but low). But they are closed-cans, so they don't have the overwhelming effects of similarly priced open-can phones, and as I mentioned earlier, it's a well-balanced set, so if all you're looking for is strong bass, this might not be the set for you.
Hope that helps sway your decision either way.
irmongoose
