2 channel vs headphones

Yep.  Headphones are the office "speakers".  Speakers three feet away on a desk is a little too near-field for me.  Let headphones do what they do best (great "nearfield").

Yes. Without additional constraints like noise, speakers are going to win out most of the time just due to the fact that their visceral, tactile full-body response and realistic soundstage adds so much to the immersion & illusion. 

Speakers as a class are also generally less fatiguing than headphones (I know there are exceptions). This definitely affects me.

High-end speakers have had WAY more R&D and materials quality put into their drivers, manufacturing, and overall design. Until not too long ago, those absolutely dirt cheap mylar diaphragm moving coils were the dominant device in "high end" headphones (Sennheiser HD600, AKG K701 etc - to be fair they still sound really good). Good on companies like Audeze & Hifiman for accelerating planar tech, and Focal for beryllium drivers. At least head-fi is finally out of the stone ages now. 

Headphones have the advantage of a controlled, consistent acoustic environment (their earcups, pads, and your head) versus the huge variability of rooms to house speakers. However, with even basic thoughtful setup, I don’t find this advantage to be nearly as significant as some claim. Some speakers are better/worse than others in how they interact with a room. You seen the little Japanese rooms with big Tannoys? That works better than you’d think lol. Also you can change the pads on headphones and get a TOTALLY different sound - so the variability is still there, if easier to control. 

Headphones DO have the advantage of being able to implement true full-range electrostatics in a single diaphragm without being the size of a room. This is what I like them for: high-end e-stat cans with a high-end e-stat amp. There’s a  true magic in there that I sometimes crave even with the option for my speakers available. My old gold standard here was Stax SR-009 out of a DIY T2 amp; that’s now updated to ES Lab ES-1a or 2a out of a T2. And I know there are even better e-stat headphone legends out there (though OUCH on the price!). A good e-stat has simultaneously the lowest fatigue factor I’ve experienced in a headphone AND the most detail. Their soundstage is also more natural to me than even the "soundstage kings" of other types: Sony MDR-R10, Sennheiser HD800, Sony Qualia 010, AKG K1000

I do. You can see my main system and headphone system under my USerID. I listen to them nearly equally... say an hour a day. 

For decades my headphone system was always so much less satisfying it was only a system of last resort. For about ten years I improved it at work in my office... I was able to have a tubed amp and separate components. I traded out many amps... trying to get the dynamics I believed my headphones were capable of delivering... I had about five flagship models... Sennheiser Focal, etc. 

Finally I invested in my third Woo headphone amp... the Woo WA5. All changed, the power, midrange and dynamics went up by a step function. Suddenly all the flagship headphones sounded more like each other and less different. All had what they needed to sound their best. While $6K for a headphone amp may seem ridiculous... it was worth every penny and makes my headphone system impress me every time I turn it on... like my main system.