I don't really have a strong opinion in the game but mind you that MongoDB is pretty darn fast http://www.peterbe.com/plog/fastestdb
At least when you're not at scale.
And it's pretty cool that you can make a choice between fast writes or safe writes. You can't have both but at least you can have the choice.
Having said all that, I generally prefer Postgres in almost every possible case.
However, this RethinkDB project looks sexy and with a great potential.
You know this benchmark is bullshit because it says memcache is slower than redis (at editing) and mongo (at creating and deleting) and motor (at creating).
And it's pretty cool that you can make a choice between fast writes or safe writes. You can't have both but at least you can have the choice.
Having said all that, I generally prefer Postgres in almost every possible case.
However, this RethinkDB project looks sexy and with a great potential.