If the Surface is basically the same as a MBA 11", why not just get the MBA 11" with a proper keyboard and bigger screen?
OT: Just today on Metro North I had occasion to open up my 13.3" MBP and do a bit of work in one of the cramped jumper seats. Even balancing on one knee, it worked reasonably. Would have been a cinch on an 11" MBA. Would have been impossible on the Surface Pro.