You’re missing the point, part 2, son. The point is that *implementing* hot-reloading is harder with concatenation. With RequireJS, it’s easy, because you simply swap out references — there is simple modularity. With Webpack and Browserify, hot-reloading is simply harder to implement — it can be done, it’s just harder. And yes, file size does matter. 800KBs is too much, it takes too long to load in development, as well as production. No matter what system you are using, RequireJS, SystemJS, Webpack, Browserify — you will want to load less than ~500KBs on first-page-load, in development and in production.