Ask HN: Mongoid vs ActiveRecord (Postgres)

So we've come up to a point in our project where we are thinking, should we have actually used MongoDB? We are using it at the moment, but sometimes find a few gems don't have support for Mongoid and we often have to find a work around.

My main thoughts are:

1. Is using MongoDB actually any better in production?

2. What are the pros and cons of using either one?

3. If you were to create a new rails app, would you use MongoDB and why?