Deciding what type of trigger depends on several factors.
What kind of effect/prop is being triggered?
Do you want the effect to go off at the front of the group, middle, or end?
Does the effect run on a controller (i.e. Fright Ideas Boo Box or similar)?
Is their an actor nearby?
How reliable do you want it to be?
How much money do you want to spend?
I for one, am completely against cheap pressure mats. Anything people can possible trip over is never a good idea and you have to worry about how to hide them. They are cheap though. And as for PIR sensors, they might as well be called P.O.S. sensors. I've installed several of these from big name companies and have had reliability issues. As for the trick of putting tape over the sensor to limit its field of vision...come on...it's like using bubble gum and shoe string to fix a prop. Yes, it's creative, but not very professional. So the only sensors I use are "beam sensors" in all the professional haunts I've worked on. Now, there are several different kinds of "beam sensors" and they each have their advantages. But if you want reliability and professionalism, they are the way to go.
Here's a tip when using "beam sensors"...Mount them about four inches off the floor. That way, you can train your actors to step over the sensors and they work in foggy conditions because...fog rises.