This review is going to come off as biased because of how ecstatic I am with this purchase. I was in no way compensated by, and I'm not affiliated with, the brand in anyway.I spent way too much time doing research between the Sony XM5, the Bose quiet comfort ultra, and the Sennheisser Momentum 4. All had their strengths and potential drawbacks. I'm no audiophile, but those I talked with recommended the momentum 4s over the Bose and Sony for quality of sound. The online reviews seemed to confirm this. My immediate reaction was the reviews were correct. The sound is excellent, and the headphones do a great job with producing the entire range (highs to lows.) Bass was minimal initially, but after downloading the app, I was able to customize the eq settings more to my liking. They sound phenomenal.One of the main upgrades I was looking for from my pervious set was comfort. I wanted something that I could wear for long periods without hurting my ears and head. I still believe the Bose were the more comfortable (noticeably lighter being the main difference.) But the Sennheisser was extremely comfortable as well. They don't clamp my head tightly, causing fatigue. This also means I won't be using them to workout, but that was never my intent for these. I couldn't justify the difference in cost for the Bose for what I considered a minimal improvement in comfort.All 3 brands offered lots of bells and whistles. Auto pause, good microphone quality... The noise canceling function was great for all 3, with there not being a big enough difference one way or another to matter to me.I had ruled out the Sonys pretty early due to the many online complaints I read about their durability- apparently their frame design is prone to breaking easily and sony does not stand behind it. Sennheisser has its own issues- they're discussed on a lot of forums. It seems they're mainly software type issues with volume control, etc. My personal experience is that the touch controls aren't quite as accurate as I would like (when I touch the sensors on the headset to adjust volume, it's hit or miss. I may just need more practice. This can also be adjusted more accurately by using the controls on your phone or computer ) This is a small annoyance to me, and not anything that influences my overall experience.Once I narrowed down my choice of headset, I went looking for the best deal.I was a little leery of purchasing anything refurbished as opposed to new, but the cost savings and the year warranty helped me to justify the risk. The fact that they were refurbished by the manufacturer as opposed to a random technician was the deciding factor for me. I couldn't be more happy with the purchase. They arrived in the box, with case and all original components. Everything looked pristine and brand new. The case seems to be well made.I love the sound quality. Again, this isn't a $6,000 set of wired headphones connected to a cherished vintage hi fi record player. These are wireless headphones playing compressed audio files, so take it with a grain of salt. But for what I bought them for, they do an amazing job and I'm ecstatic with the purchase. I would by them again in heartbeat.