After traveling with a 15" laptop for a couple of years (more often than not in FC), I went to a 14" Lenovo T43 when the time came for a new one... and that was a deliberate downsize. I find the difference, however small objectively, to make it much more convenient for in-flight work... heck, when folks in FC recline into your lap the space gets cramped. And it is also that much easier to fit into a smaller laptop carry case.

Sitting here in the home office now and have never felt the need for anything larger. Much of my life is wrapped around website reviews and power point presentations and the 14" screen is just fine for both. Yes, I enjoy a larger screen when I do work on one but for overall moving around the country, this size is just fine.