Security through obscurity is never a good thing, this has been proven many times over.
Basically, both models have been set to the test years after years, open source software always wins in regards of security over closed source solutions. Security holes are patched faster, and in most cases, way before they’re even exploited.
Other benefits are… well, you can change it however you like… or pay someone to change it (not so uncommon as some might think).