All my information is second hand and comes from guys in the exotic deer industry who build fences. One day I plan on raising exotics and plan on fencing in 60 acres of 8 foot tall deer fence. Every one of the ones I've spoken to have told me that a post driven into the ground is stronger and harder to get out then one set in concrete. I've been told that they have done both, side by side, then come back a week later and pulled them out to show their clients the difference. The post in concrete always comes out easier. They also prefer metal over wood. I'm a wood guy and this has been a real issue for me to overcome, but I've finally reached that point where I'm going to use metal for my corner and H brackets. They say to go 5 T posts, then put in a 2 3/8 pipe for the runs, H brackets for any changes in elevation and for corners, to pound the anchoring post into the ground at least six feet and weld the diagonal support pipe to it.
The other big lesson that I've learned from my neighbor, who fenced in about 120 acres of his land five years ago is to make sure all the trees are removed that are close to the fence. His fence is in terrible shape from all the branches that have fallen on it, and I've only seen a small amount of it. I'm in the process of removing every tree within 30 feet of where my fence will go. EVERY SINGLE ONE OF THEM!!!!
Sadly, I've learned that saving a tree never pays off, and sooner or later, it will have to come out anyway, usually after it's started dropping branches, or dies on you. Every single tree that I wanted to keep, but ended up taking out, I've found that I don't miss it. Better to get it out when it's easy then try to keep it and deal with it when it's harder and more expensive.
Eddie