I switch to bloom during flower, bloom has some other goodies in it to increase trichome production as far as I am aware..
Original: Urea, Phosphoric Acid, Potassium Silicate, Sodium Molybdate.
Bloom: Urea, Phosphoric Acid, Potassium Silicate, Seaweed Extract (Ascophyllum Nodosum) and Potassium Hydroxide (extractant), Zinc Sulfate, Boric Acid.
I have seen the claim to lower stretch, I did not notice a big difference using psi/psi bloom at recommended dosages in soil. I did see thicker stems and a huge increase in trichome production. I am just starting to sample some of my current harvest (first with psi) and the taste of the sample buds is big time flavor increase..
I can say I thought I would be tossing both as I tend to be skeptical about all the liquid magic brands come up with but psi earned itself a place in my grow.. I may even try lush (when my current kelp is used up) or some of their other products launching soon