If you're looking to simply keep two DNS providers in sync, you can just set one up as a Secondary DNS. Dyn provides this as a feature and that keeps our DNSMadeEasy and Dyn accounts synchronized without having to think about it.
It also doesn't help with managing the records in the primary provider, requiring either working in a UI or writing using software like OctoDNS to manage it. It's definitely a good option for simpler and stable setups, neither of which is the case for us or many of the people I've talked to. If it fits a situation you have it's worth exploring.
There's an article on ZDnet, http://www.zdnet.com/article/github-open-sources-octodns-new... that does a good job of covering some of the reasons for it that is probably relivant to this.