The Tria is an actual laser system, while almost all other products I found were intense pulsed light. Having a laser diode means much better directing and targeting of the energy, as lasers have almost perfect collimation, and they can pick an exact wavelength. IPL is not laser based so the light cannot be directed nearly as well and it's going to produce a lot more wavelengths in the spectrum (I think much of it's filtered out from my research).
That and it is FDA approved, a lot of the devices aren't, and when I'm exposing myself to high power radiation of some sort, I want to make sure I'm not causing damage to more than my hair follicles.