Someone neatly wrote up the main advantages:
http://cramer.io/2014/05/03/on-pull-requests
Phabricator's issue tracker is also an excellent choice over GitHub's simplistic issue tracker.
Also, Gerrit isn't that hard and I've seen small teams get productive with it within a 1-2 weeks.
No need to reinvent the wheel!
By the way: I live in Europe and I haven't worked for one single company which would allow their developers to host proprietary source code with a third party SaaS provider.