For sure Angular 2 will get most popularity from the Angular 1 project (and this is why, IMHO, they decided to stick with the "Angular" name for a completely new project). Anyway, Aurelia seems to be a nice project as well. First and foremost, Durandal Inc., the creators of Aurelia, is planning to serve first class tech support for the product. Another notable feature is that, as Rob Eisenberg himself says, most of Aurelia is replaceable if you need some feature that some other library has. Also, I remember Eisenberg telling that Aurelia will be much slimmer than Angular (about half the size, IIRC?)