This is rather an odd thread, like launching "cars vs motorcycles" ... on an automobile forum. Given that there are over 35,000 posts for speakers and under 500 for headphones, it's not exactly surprising that most of the (few) responses here have favored speakers. If someone posted "headphones vs speakers" on head-fi, the responses might just possibly be a bit different.
As a few have pointed out, they're completely different listening experiences. Cars and motorcycles.
A more interesting conversation might be to ask why headphones and iems have taken off in the last decade. There's a surge in the headphone market not seen in that of traditional stereos. A lot of this growth is young people, and I'm not talking about earbuds and iPhones. I spend time on head-fi and I'd guess that if we compared the number of posts by people under 40 in a given week, Audiogon might not exactly be crowing. We can be critical of their preferences (speaking as someone who has haunted stereo stores for half a century), but headphones is where the action is these days.
I'm with the posters above who say both/and. Headphones are a lot of fun.

