I have used webpack and browserify, and I am currently examining rollup. What stuck out to me for rollup was the smaller footprint vs the other 2: https://github.com/nolanlawson/rollup-comparison. Rollup allows you to easily use ES2015 modules similar to JSPM,however according to their site JSPM is meant more for application development rather than module development. This is confirmed in the fact that JSPM may be using rollup internally in the future: https://github.com/systemjs/builder/pull/205. If you are concerned purely with module bundling, you want a small footprint, and you want ES2015 syntax but build towards every format, you can't go wrong with rollup. If you are more concerned with building an application then you'll probably want to gravitate towards the other 3.