Sure, but what about responsiveness and other metrics? Reducing the absolute amount of data sent over the wire may be what you are optimizing for, but it's not

Sure, but what about responsiveness and other metrics? Reducing the absolute amount of data sent over the wire may be what you are optimizing for, but it's not by any means the absolute metric of performance. Personally, as a user, for many web apps I would rather see a longer initial page load but have all subsequent actions appear instantaneous (a la Gmail), than spread the load times out across every action. My point isn't that SPAs are better than traditional web apps or anything like that, just that these decisions depend entirely on what you are optimizing for and what your priorities are. If initial page load time is your priority, then an SPA may not be the way to go; however, if your goal is to maximize responsiveness or interactivity, then the extra 2MB of JS will likely pay off.