Im trying to make a wall and I need some tips on what to train, so what is better for a ferrothorn?
252 hp Ev's and 128 Def / Sp Def
255 Def / Sp Def
The First one, which is the 252 HP, 128 Def, 128 SP Def since this will be a Support Ferrothorn. This would be good because if you use the other one, it would completely be destroyed by a Fire type(example Infernape). Leftovers is a great item for it to take advantage of that HP. I would suggest using Substitute if it can learn it, and Leech Seed. Hope this helps..
/ 252 Defense / 252 Special Defense / 4 HP /
The HP investment looks tempting, but having a lot more HP over Defenses actually weakens your bulk. Only fully invest HP if your Defending stats are about 20 points within range of each other.
Pokemon like Dusclops have proved that jamming a lot of Defenses (130 in both) into a little HP (40) makes for a bulky wall.