I can talk to this. This past season I bagged both a Tournament Harp and a Neutron Particle. The way I describe it to people is that if you know what a Harp does (oh my god it's so overstable. . .), then a Particle is basically 0.6 Harps. It does what a Harp does, but not as much so.
For a more practical example, Harps fight HARD out of anhyzer for me on RHBH. They want to fade to the left, desperately so. A Particle, on the other hand, will fight out of an anhyzer, but not so immediately, so I can shape some tasty, tasty lines through dense trees with them.
edit: I imagine if Ricky was throwing Particles, they'd flip up to flat, have a little turn, go straight for a while, then finally dump at the end, all the while covering double the distance mere mortals throw them.
How about an MVP Deflector, would that more beefy like a Harp?