TLDR: Rollup and ES modules give us:
- smaller bundles due to tree-shaking and scope-hoisting, and
 - faster runtime perf than CommonJS, by avoiding runtime module resolution
 
Sources to back up these wild claims:
- Rollup
 - PouchDB 5.2.0: a better build system with Rollup
 - Scope-hoisting in Rollup
 - rollup-comparison
 - The cost of transpiling ES2015 in 2016
 - Angular 2 hello world smaller than Angular 1, thanks to Rollup
 - Tumblr perf audit, Browserify module resolution taking 400ms on a desktop machine
 - Imgur perf audit, same story
 
sadasd