For my uses, amateur music production, gaming, movies, most types of music, audiobooks, etc.
And thanks for the advice, I ended up going for the M50x since my brother already owns the Sennheiser HD 598 and the m50x were bundled with a TASCAM DR-05 portable digital recorder worth $90 on amazon for free so I bit the bullet. In my opinion, for the price to performance ratio these two models are at the top of the heap. In terms of performance, I directly compared both the 598 and m50x and both seem to have pleasant mids and highs, the Sennheiser has superior mids and I could hear a slightly greater depth and clarity of detail in this range. The ATH had a slightly punchier bass and drums sounded a bit crisper to me. The Sennheiser's are without a doubt more comfortable but leak a lot of sound and don't have much sound isolation whereas the ATH have decent sound isolation and don't leak nearly as much , while still comfortable to use for hours on end. If you're looking to wear what feel like clouds, the Sennheiser's are remarkably comfortable whereas I would describe the Technica's as comfortable. The Sennheisers also have a wider sound stage, and an overall more mellow profile whereas the ATH have a tighter stage with a more aggressive sound profile- in spite of these differences, overall they both sound more similar than they do different. To me, for someone who prefers acoustic and classical music, the Sennheiser's sound incredible, and perform well for electronic and other types of music. The M50x sound a bit more intense,crisp and booming for rock, jazz, movies, electronic etc. but not distorted like Beats while performing well in both acoustic and classical types of music. Finally as far as headphone construction, both are very durable, but the M50x definitely has the edge with the ability to collapse for portability, and the detachable cords are easier to manage than the Sennheisers. The biggest difference is the super-wide sound stage in the Sennheier's which comes at the tradeoff of 100% sound leaking and little sound isolation, making them not ideal for public use but having the edge in a private setting. You really can't go wrong with either, and for my uses the m50x suit me well. Once you find a quality headphone in the $200 range it seems to come down to subjective taste more than one being ultimately better than another.