After many gaming headsets i finally gave up and decide to go for high quality sound. i like closed back more than open but if the sound is better with open then i will go for that. I have a few headphones i dont know what to buy. ATH-M50X, DT 770, AKG K702, Philips Fidelio x2, sennheiser hd598. I have a budget of 100 euro BUT all these goes for like 70-100 euro on ebay What i mean about allround is like music, movies and games.
open headphones generally have more "soundstage". they will generally sound more open, airy with more depth (distance variation) to sound. closed headphones generally have less so may sound a bit closed in and intimate. this is a generalization as it is not always true but is correct most of the time. open headphones would be like listening to a band in a park amphitheater while closed cans would be like listening to a band in a bar.
closed cans will passively filter sound from leaking in and out while open cans will not. closed cans often tend to be more bassy than open variants though this is not always the case.
headphones also may have different signatures or response curve (how they sound). some are bassy, some are neutral, some are bass light, some do a bit of bass and treble but lack mids, some are mid centric. what type of response you like depends on what you listen to as well as personal preference. generally neutral is a bit more easy listening and is the most tonally accurate but may sound dull to some. bass light is good for gaming advantage but can sound boring to some due to lack of bass impact. bassy cans generally hit hard but sound muddled for everything else. v-shaped cans are the most fun sounding but will lack mids. mid focused cans will be great for mid centered music and some vocals but will lack on the bass and treble end of things.
the m50x is v-shaped, in the bassy classification but not bass cannon level, is capable of sub-level bass yet has decently clear highs. overall good sound quality but has a very small soundstage. things will appear to sound very close to your ears without much depth. the earcups are also on the smaller side. i have a pair myself and while i dont mind the lack of soundstage (i use it more for music) you might not agree.
the dt770 is similar to the m50 but overall would be considered better. it has a decently wide soundstage (for a closed can.. its not the same as an open can) with a bit more clarity and bigger earcups. you might want an amplifier or soundcard for it though.
akg cans tend to be from bass light to neutral in signature. they sound best with a good amp and good source.
the x2 is a good can as well but i'm not so familiar with it to give a comparision.
the 598 is neutral sounding, decent soundstage, decently comfortable. it is a bit slow which makes it good for easy listening (no fatigue) but might sound a bit boring to some.