For some, it's not set right if it's not set in concrete. For others, only driving will do. And what about how deep it should go? Whether digging or driving, nearly everyone has an opinion about how deep a post should be. If you can get three fence installers to agree on all these issues, there are a few countries in the Middle East that could use your unique talents as a mediator.
The fact is, we live in a great and varied world. Conditions in one area of the country are not the same as those seen by fence installers in another area. Sometimes the conditions change so much just crossing the street, or even in one backyard that what works in one place will just not work in another. In order to be a complete and well rounded professional, it pays to have several techniques available for setting posts.
While depth of post depends on variables like soil stability, the potential for frost heaving, the height and type of fence intended, and the materials used, the method of connecting the fence to the planet can vary due to all these factors, plus local digging conditions, water table depth, and personal preference of the installer.
It boils down to one basic point. There is no single “best way” to install a fence post. Some ways work better in some areas, and some don't. That's why there is so much varied opinion, and why it is important for the consumer to make sure they hire a professional fence installer. A professional will have several methods available, as well as specialized knowledge of the conditions in your area.