They're about as reliable as one another. From what I've heard, though the PDI's adjustability is neat-o, you can't make it as light as the Zero-trigger.
However, springs do occasionally need to be replaced inside of all triggers. The Zero-trigger is supposedly a heap of mess inside that makes it really hard, while the V-trigger is a little less complicated. Those who actually own the Zero-trigger also say that all of the disassembly instructions are in Japanese, while PDI's instructions, and their CS, are in Chinglish.
Also, ^^ yes the PDI is $150, but the Laylax is $145.