The Yoga 2 and Yoga Pro are very good, cost effective, but a little bit heavier than the MS Surface Pro 3. The thing with the Surface Pro 3 is that it isn't a "laptop" it is a tablet with a keyboard, I like the keyboard for what it is, but I would never code full time on it (or use it as my only PC).
The MBA is wonderful, really just wonderful, I have nothing but good things to say about it as a small light laptop. It is a little expensive but the touchpad is darn good and the keyboard is also a pleasure.
I'd strongly suggest you head down to Best Buy. They have the Yoga 2, Surface Pro 3, AND MBA. So all three of your core options. Get a feel for the weight and the trade-offs.
PS - I own a Surface Pro 3, it is good, but it is ultimately a tablet that can run x86-64 applications, and even with the kickstand it isn't as usable as a "real" laptop. Plus the dock is super expensive in its own right.
PPS - Given your list and your requirements I suspect you'll get the MBA. It is the "boring" option but something can be said for just getting something which will simply work and is popular enough so you'll get good driver support on Ubuntu.