Jirachi is probably the stronger option. Though Tinkaton has access to Gigaton hammer, Jirachi has serene grace, which doubles the secondary effects of moves. That means Iron Head, instead of a 30% chance to flinch is 60% while Zen Headbutt flinch chance increases from 20% to 40%. Jirachi can be annoying with the ability and it doesn't really matter about typing, they still have the same weaknessess.
