I'd say Ferrothorn is a better choice, and its all depending on what you are looking for in those Pokemon. Both are excellent walls, that set up entry hazards such as Spikes, and Stealth Rock. Not to mention both can Explode. The only difference between the both is Ferrothorn for instance is more like a bulky wall, especially which leech seed, sub, paralyze, and leftys'. While on the other hand Bronzong can be a bulky supporter with Light Screens, Reflect, and etc.