These are such personal decisions due to a person's age, eyesight, app selection, app use, sole computer or not, battery requirements and so on, that threads about preferring 11 or 13 ought more be what size suits your specific needs best.
i personally chose an 11 MBA after previously owning a 13 MBA but a short while and enjoy the enhanced portability. It is not my only Mac computer, being a lifelong Mac user. I have cinema displays, MBP laptop and an old desktop machine at my disposal. These remain on call at both my home and office. My apps and manner of working indeed are better served by a larger monitor, but the size monitor that suits me best exceeds the 13. So therefore, I opted for the most light, portable and, therefore, "fun to have with me perpetually" 11 inch size.
Given that my periodic days traveling require bringing all manner of items to see clients, the conundrum presented itself as to whether to bring my 15 MBP along or not. I always regretted not having it with me. Now, it's a no brainer because the 11 is always with me, fitting into non-laptop style bags of small dimension or hand carried like the way people tote their ever-present iPads. I do seem to get more done, being able to compute on a moment's notice when inspiration strikes.