kinda joking but really systemjs is (a) a bit more standards focused than webpack (if i'm not mistaken) and (b) a lot easier to set up
systemjs is a few things. its a package manager via jspm where webpack uses npm, its a module loader where webpack just gives you the chance to plug in various loaders, and its a bundler, which is mostly what webpack is.
for this reason, systemjs is a bit more of a one stop shop for module loading, and so configuration and set up is quite straightforward
whereas webpack is more designed to solve general front end problems, and you can solve tougher problems with it, for example better css bundles, but it also requires a great deal of configuration and set up
i have an entry point like this: System .import('app/bootstrapper.js') but when I bundle it needs to be this System .import('bootstrapper'), I was thinking about using the has function to determine which one is valid is this best practice?