Trifoliates (or whorled pyllotaxy) happen every once in a while, and just like 'purple' genetics...they're nothing special, beyond the intrigue. They do not grow fatter, they are not psychotropically stronger, and they don't taste any better than it's 'normal' sisters.

Best advantage (and possibly the only advantage) is that early-on they have 50% more surface area to collect the light. Once the plant fills-in, it doesn't matter any more, and often during the maturation process the mutation disappears. (resumes normal growth habits)

Over the years I've had quite a few trifoliates develop prior to switching to 12/12, and even had one develop after switching. Exciting at first, but no big deal.