Has Trigger mentioned that he wrote this review article? A bit disingenuous to post it as a reference without disclosing his bias.Here's a recent article, which covers all the important aspects of aquarium LEDs, including PUR, and the science behind it. The website also reviews many of the more popular aquarium LEDs out.
LED Aquarium Lights,[censored]Lighting; How they work, DIY | Aquarium Article Digest
Here's a good review as well.
TMC AquaRay Vs. Build My LED | Marine Aquarium LED Study