I know this questions can't be answered, since it depends on so many factors, but let's call this an opinion survey.
Fence will be 5' high, with a 2x4 pressure-treated pine (PTP) wood frame and horse-fencing "panels". Posts will also be PTP, 4x4. Stainless steel fasteners, to avoid corrosion due to the PTP.
Something like this, but with slightly thinner/flimsier wire: 
Ground is mostly clay, somewhat acidic (pH about 6.5), not impermeable, but also not the most permeable stuff ever.
Since the majority of the surface area is horse-fencing, I'm not expecting the wind to be much of an issue.
Of the following two options, which would you go with?
- Use 8' posts and bury them 3' deep, tamped-earth, with gravel at bottom for drainage.
- Use 5' posts, anchored at the base to a hot-dipped galvanized post base, either something like an Oz-post T4-850, or a Simpson CB44HDG embedded in a concrete footing?
My main concerns would be:
- Rot/corrosion. Which will deteriorate faster, a buried PTP 4x4, or a HDG anchor in contact with corrosive PTP wood?
- Cost. The HDG anchors are expensive! Are they worth it?
- Time. I'll be digging by hand (digging bar and post digger).
- Warping. The PTP is very green, very wet. Will one of these two options deal better with the inevitable warping-stress?
What do you think?
