[stevendgarcia]

I think it depends on what platform you choose. For my Ruby/Rails work postgres support has been nothing short of phenomenal. The addition of JSONB and hstore added the dynamic schema features of MongoDB that I'd used in a previous projects. Nowadays I miss none of those features, plus I get free fulltext search, Common Table Expressions and tons of other vetted goodies that come with postgres.

However, working with NodeJS was a different story, as there seems to be a lot more community around projects like Mongoose as opposed to Sequelize. I found that bootstrapping a project from scratch was a lot easier and the pace of development was relatively hiccup free. The only downside for me was memory consumption. Mongo stores all data in memory for fast reads and this quickly proves unsustainable if you aren't prepared for it. By comparison, postgres has some sort of crazy developer voodoo behind it because it has way more features, yet consumes far less RAM and is more resilient to failure in my experience.

NOTE: I haven't built a Twitter or anything "webscale" Most of my apps are for small to mid sized business so take my input here with the appropriate grain of salt