If I didn't live with a bunch of people while i'm studying, I'd be more likely to spend on some really nice speakers. But, seeing as i'm up late, and speakers are loud and annoy other people, headphones will do. Not to mention, spend a couple of grand on headphones and you get something special, spend a couple of grand on speakers and you get 'nice' speakers. And speakers are only a tiny part of the equation, if you're going to go all out on headphones, you buy gear, connect it all, burn it in, proceed to sit anywhere, and enjoy. Speakers, you need to select gear, make sure it all plays nice together, then make sure that gear plays nice with your room, if not, enjoy average sound or $$$ fixing your room so you can sit in one place and enjoy musical nirvana. Not to mention that if you want to lie down, it comes at the cost of your audio nirvana. Can't count the times I've lied down on the couch, closed my eyes & drifted off into the music from cans.
And for gaming, the ATH 7000's come out to play, no speaker system could come close. Nothing like being able to hear the footsteps of someone running behind you, or around a corner 30ft away. Speakers just can't come close to nice wide open cans for twitch gaming. That hyper detailed presentation with a decently wide soundstage is really, really nice. Not to mention the hassle of setting up a 5.1 setup for my computer, would be a nightmare.
Then there's the slam vs detail aspect I guess, Speakers do bass that you feel, which makes the music have that much more body and physicality, my my lcd-s do bass well, and as far as headphones I've tried, they have the most 'physical' presentation i've heard from cans. But while I appreciate it, and my ears certainly feel it, I don't feel it in my gut, i'm having a party in my head (and a little bit off to each side), and my body's not invited.