What are the differences betwen using xtypes and the Ext.create() way?

I am asking, because, i was trying to build an app based on ST 2.1. In develop mode all worked fine. But after using sencha cmd to build (minfier) the app
sencha app build production
i was facing the fact, that nearly no view was working. e.g. jsonp requests were successful, but the corresponding lists show nothing

after some tests, i recognized the problem has something to do with using multiple view files. if i was putting the whole view stuff in one file, all worked fine in developmode and also after builds.

the comments in the docs gave me the needed hint. here (go down to comments) the user talwinder is posting a solution

I was using Ext.create() to instantiate a class/view. After using xtypes all works.

thanks to talwinder