If I had the choice I'd definitely use all metal, but if you know your horses that you'll be using it with won't run into the walls, the wood will work great. I made a 50' roundpen out of wood. I used the $2 landscape timbers from the Home Depot for posts, a half bag of cement and put them down about 3' into the ground leaving 5' up top. Then I went to the sawmill and got 1"x6"x8' boards for $1 a piece and put 3 boards. One at 1', one at 3', and one at 5'. Then I put a gate to get in and out. Very cheap, very sturdy, but the only downfall, you can't move it like a metal roundpen.