If you get frost in the ground where you live, you have to pound them in, otherwise they will pop right out the next spring. Even using concrete they will pop right out, and actually worse so because now the frost has something to grab hold of as it pushes upwards.
I do all my fencing in the spring of the year. I use a bulldozer, but a rented excavator will also pound them in.
I would use nothing but pressure treated posts and woven wire fence just because it is so cheap. It might take 3 days to put up 3000 feet, but what the heck, 30 years from now it is still up, and no having to maintain juice on those 3000 feet at all. What Pressure Treated wooden posts and woven wire costs...divided over 30 years, makes it the cheapest fence by a LONG shot.