[JepZ]

You are right, they are not exactly the same type of programms. Nevertheless, most of the time they are used for the very same thing: to transform your development source to format which is best to be delivered to the browser (bundling).

Actually, I still use Gulp to call Rollup.js as it is more flexible and allows me to use features which are not the scope of Rollup.js (e.g. automatic browser reload). My point is, that the exact thing Rollup.js focuses on is very important for the long-term development of JS: Modularization. Yeah, I know thats an upcoming part of the JS standard. But with Rollup.js you can use it today, as it has various adapters for legacy formats and therefore you have a tool which allows you a smooth transition into the future ;-)

[vladimir-y]

Sure, but just don't limit yourself by the Rollup.js only. Again Webpack is a module bundler (modularization is there), and it was a module bundler before Rollup.js went public. So you can use all the ES6/7/TypeScript stuff (including modularization) using Webpack, Rollup, Fuse-box, and other bundlers, the difference is in the configurability, performance, configuration syntax, etc. Though yes Rollup provides some specifics, which might be more suited for the standalone libraries releasing, while Webpack would be better choice for the complex app development (that is it not supposed to be released as a library, but deployed somewhere as a complete app).