IMHO I dont think pk 13/14 is really a fair comparison.
In most cases, like with Hesi PK 13/14 for example, you would not start using PK 13/14 until week 4 of flowering at the earliest.
In most nutrient programs that I have worked with, PK 13/14 is only used once during flowering for a few days up to about a week, and in other nutrient programs like the one I just mentioned here with the Hesi product, it is not used at all until week 4.
Koolbloom (liquid) on the other hand is meant to be used for the ENTIRE flowering period, and then you would add the Koolbloom powder to the mix for the last 3 weeks for ripening and "stacking" effects. With this information, I would consider comparing a product like PK 13/14 to products like koolbloom a "apple to oranges" comparison.
Dont get me wrong, PK 13/14 is a great additive to have on hand for flowering and I guess you could use it as a flowering booster for the entire flowering period if you wanted to, but my experience with using it only once for about a week has shown to be the best way to use a product like PK 13/14.....IMHO.
One of my favorite KISS nutrient programs is to use PK 13/14 once during week 3 or week 4 of flowering depending on strain, and use liquid Koolbloom from start of flowering to the start of flushing, and of course adding the powder koolbloom for the last 3 weeks......During week 3 or week 4 that gets the PK 13/14, I cut the koolbloom dosage in half for heavy eaters and cut it by 75% for finicky eaters during that one week when PK 13/14 is applied.