For the vast bulk of stuff that most people will want to do on a computer, though, most of the time you don’t need a desktop monster. I don’t think you even need a 15” screen, which is essentially a portable desktop. You just have to use a small screen productively.
Let me tell you a bit about how I do that, with some recommendations as to best practices and some utilities you might want to look into. - Matt Gemmell
I'd argue his proposed setup works on every Mac, no matter how big or small your screen is.