Отличие только в названии, которое и сообщает дополнительные возможности.
Но по настройкам они идентичны.
The NiParticleSystemController animates an NiParticles-based object. The controller handles particle birth and death, spawning, and motion. It also includes a framework that allows classes to create other effects. NiEmitterModifiers will allow time-based manipulation of the NiParticleSystemController object itself, while NiParticleModifiers allow time-based manipulation of individual particles.
