I suggested Parse because I'm personally using it right now, so I know it well. That's obviously a bias, so take it as such. Firebase looks very similar. If you are going to lean on the greater community, Parse seems slightly better, because of the fact its a fork of Backbone-more people should understand pretty easily what's up with models.

Also, Parse is owned by Facebook and has pretty solid, simple login and integration with social sites.

I've tinkered with Firebase and looks quite comprehensive as well. From what I can tell there isn't much difference. They have a nice little wrapper for Angular too.