The clown is going to be one of the more (Queen's and undulates seem to rule the roost) aggressive triggers out there, but every one has their own personality. Niger's are one of the more layed back triggers. Bursa's-middle of the road.
Triggers are cool and it always gets back to individual personality, but let's face it, in general, comparing aggression is like assessing the damage between a land mine and a fragmentation grenade: they both do damage, it's just a question of how much.