Except in volume. ( I have HD555's with HD595 mod, they start cracking at ''-9db'' at some loud songs)
Except in feeling.
And less configurability, some music I prefer to have more lows, some music I prefer more flat like sound, and also depends on mood. I have an active sub on pre-out from A/V receiver, which I can adjust independently from the rest, which is impossible with headphones. No headphones will make my room shake.
I dropped the centre speaker myself, I have a 4.1 setup which I often use in 2.0 or 4.0 ( dual stereo) mode. Center speaker is useless for music, and unnecessary for films imho.
As for gaming, 5.1 support is great in some games, and rubbish in others, I must admit 5.1 worked very well in many games and I could clearly hear people behind me from rear speakers, but I don't game that much anymore and always listen to music so meh.