Grounding is probably one of the most controversial issues in electrical construction. When I was setting up services for cell sites in the 90's, I had to go to just about every municipality in the Chicagoland area and meet with the inspectors to explain what we were doing. Cell sites have their own grounding requirements and most inspectors were clueless about this new technology. When they started failing our work, I decided to be proactive and meet with the inspectors before the work began.
Grounding was a major part of our discussions. Some inspectors wanted the service to be grounded to a cold water pipe and a ground rod. Others said one or the other, never both. We have theories about what goes on in electrical grounding but I don't think anyone really knows 100% for certain. I've seen electricity do some pretty weird things no one could have predicted.
In the end, the easy answer is to follow your local code. If in doubt, call the inspector. If anything goes wrong, blame them.
“Travel is fatal to prejudice, bigotry, and narrow-mindedness..." - Mark Twain