These headphones can be found in any studio for a reason. They are affordable (less than 100$), they have flat response and isolate well (monitoring) and sound good, maybe not compared to some more expensive models, but still, probbably the best in the price range. These are also suprisingly comfortable despite beeing more on ear than over ear (maybe my ears are big?) because ear pads are really comfi and soft, but are looking fragile. Headphones also fold nicely and have a pouch included with them. Compared to M50s, they look fragile, but are made of metal and should do well, unless you abuse them. 
 
I would look at these if you are looking for closed-back headphones on a budget, especially, if you want to use than as monitors or even mixing (flat response). If you are willing to spend more money on closed headphones, you may want to check out Beyerdynamic DT770 (detailed but bassy), but these should work for most people.

Why do I like these? They are comfortable (compared to M50s IMO), they have really big sounstage and they really flat frequency response which I really like. They also come with nice stand that will keep your headphones "stored" nicely. Build quality is pretty good, but these aren't really ment to be travelled with. They are really big and can't fold at all + they also don't come with any kind of box/pouch, so these are really ment to be used at home. Another reason for that is power; they need quite some juice to sound good. They will reach some volume even with phone, but it won't sound very good. They work with Focusrite scarlett 2i4's amp pretty good, but I'm sure they will sound even better with nice amplifier. They are also open, so you don't want to take them to a train or something. 
 
I would recomend these for home use with some kind of amp for music listening and mixing (why I like them), but wouldn't use them in public since they obviously don't isolate very well. Iverall, really nice headphones I would recommend to a friend (unless he wants to use them on a go).

Why I like these is because they are really versatile; with many headphones in this price range, you'll need an amplifier to get them to sound really good, but M50x don't need an amp and still sound good. They also look nice, are nicely foldable and are quite comfortable. They are well built and look pretty sturdy, so they don't seem to fall apart any time soon. Soundwise, pretty good even with my iPhone, it's just that they are not flat enough for mixing IMO (too much bass).If you are looking for a nice set of headphones for general music listening and you don't want to carry an amp with you, there's good chance you are gonna get these especially, if you want closed-back headphones.