From what I know, and keep in mind it’s not much:)
They are not exactly same but overlap in a few areas. Both say they pull organics but do it in different ways. Purigen says it pulls ammonia, nitrites and nitrates. And it can be regenerated. It is not replacing carbon but can be used in conjunction. Blue is more widely used in my opinion. It is like a juiced up carbon that also attacks phosphate. I look at it as blue is a bit better, but it’s personal opinion