How exactly does a choice item hamper ferrothorn? Spikes is spikes, Gyro Ball with a Choice Band isn't bad (I assume you're using Choice Band...) and neither is power Whip. Leech Seed/Protect you can't use I guess but that's not terrible.He has Trick, end of discussion! So many times has Ferrothron come in or Blazekin (not that he matters anymore T_T) or some other setter upper come in to get a big fat Trick in their face.
Levitate Air Baloon Bronzong, that's genius! :o Everyone will think it is a Heatproof one and not attack it with fire attacks immediately and try to pop the baloon while it is Levitator anyway, possibly wasting 2 turns (pop + missed EQ) :o Meanwhile you can screen or hypnose or TR or whatever :oBalloon can help it actually using(or faking) both it's abilities in a way. Even a levitator can use it and trick with it in multiple ways!
Technically it has a water weakness under Drizzle...Under Drizzle Levitate Bronzong has no weaknesses, pretty sweet.
There's some competition, yes, but I don't think either are outclassing each other. Bronzong's usable Special Attack, ability to set up Trick Room and Screens, Levitate, and the power to not die from nearly any Fire move all set it apart. Ferrothorn has Spikes, Power Whip, more residual damage through Iron Barbs and Leech Seed, and possibly does even better in Rain.Bronzong faces some stiff competition with ferrothorn. Both can gyro ball amazingly, and both can set up. Both are weak to fire and work in rain teams, and both have wonderful typings. Bronzong IMO is better because he has access to trick, which can ruin a ferrothorn permanently.