We probably need a little more info about your project.
What type of soil are you in?
What type of fence? (how many strands?)
What type of fence posts (corners) are you using?
What are you trying to keep in or maybe out?
I use dry sack concrete mix (tamped)with water poured on top.
Some folks like pea gravel tamped in.
Don't see any using just dirt, but if thats all that is available....
We use four strands of high tensile, all electrified. Ends and corners we just tamp, we also double brace all ends and corners. Some areas we use barbed wire. They are also tamped, single braced. All new fence, and repair/replace old fence, we're going to high tensile.
Yep, dun's right (as usual ;-) ) High-tensile is some good stuff. Great if it's by trees, or where deer will tear down other fences.
Whatever way you choose to go with for your posts- just make sure that you set those corners well. That's the life of your fence. If you feel like it's overkill, it'll probably be just fine.
All of our corner braces and line braces are welded out of 2-7/8" pipe with a brace post about 8-10 feet away and a stinger about 8' from that. All steel posts set 3' in ground in concrete (we have DEEP sand here).
If a brace post gives even 1" or so you'll end up with loose wires.
LOT of work and inconvenience to have to re-do brace units and re-stretch wire... ;-)
High tensile should last as long or longer than barbed. It has a class 3 galvanized coating. As far as strength, we've had two cars go through our fence in the front of our property. Neither time did the wire break. Fence post snapped, stays came out, but the wire held. Restretch and reattach, and it was good as new.