doogles, I use an old version of Cobook to do exactly what you're asking. The latest version of Cobook killed functionality of fully synching between accounts (what Cobook calls "destructive" because it literally makes changes in a Gmail or iCloud contact entry). It was the worst thing Cobook could have done for people like us. I'd pay real money for them to bring that feature back. I'm afraid my old version of cobook will soon wither and die and no longer work when Google or Apple changes how they update contacts. The old version of Cobook that still works as we need it to: Cobook 1.3.4 (1335) - Circa November 2013. This older version of cobook even grabs profile photos from LinkedIn and Facebook and updated my iCloud AND google contacts accordingly. Brilliant.
New version of cobook only "unifies" the "view" of disparate contacts across cloud services like LinkedIn, Facebook, Google and iCloud. It doesn't actually synch anything. With the new version of cobook I can't even automatically synch, say, the profile photo from Facebook to a contact in google EVEN IF I'm using Google as my only contacts group on iOS and Mac OS devices.
It's a shame because I use Google services like Google Voice daily via the Google Voice app or the google voice web interface. I also want iCloud to be my primary address book so that I get all the iCloud address book fields normalized across all contact entries across all iOS and Mac OS X devices.
Cobook threw away a killer feature that was worth a lot.
Still looking for this Google Contacts <-> iCloud contacts synch feature via either a software running on Mac OS X or some other third party cloud service. Maybe we should all get together and crowd source funding for this need.