All fence types have their advantages and disadvantages, their fans and their detractors. Highly visible, wood appears intimidating to horses, discouraging them from crashing into it. They're seldom painted, however, saving on maintenance costs. In addition, wood can splinter and injure a horse either by fine splinters through rubbing or leaning, or by large, dangerous splinters driven in through a hard impact. I don't like it for horse or cattle property.
Planks come in several widths, thicknesses, and colors.
If put together and installed correctly, they last a right smart time. If there is any kind of impact, they have some give, but when they stop giving, they splinter, then they're like broken glass and very dangerous. They are great for geldings and quiet mares, but are not sturdy enough for stallions. Horses usually won't chew on it, and it's very strong. Cost is fairly expensive.