Honestly this is the first time we hear of PostGIS, as we mainly looked into NoSQL databases, due both to previous experience with MongoDB and the fact that we found some big services that have used it.. Curious, what have you found that PostGIS does better? Is it a preference for SQL vs NoSQL?

LOL. I'm actually on the reverse side of you. I heard about PostGIS and never knew MongoDB can be used for spatial queries. The main appeal to me is that since I need SQL anyways, PostGIS would be a simple add-on instead of having to manage another datastore. I guess my choice is more of an accident of history than any specific reason. Had I started with MongoDB first, I think I would have gone your route as well.

PostGIS is a mature and fantastic spatial database (extension), I can highly recommend it.