I'm in the "not fond of Kingsford Pro" camp; it's okay for burgers and hot dogs — stuff that cooks quickly — but for anything that takes longer it just doesn't last. For instance, I regularly cook chicken on the rotisserie, which takes a bit over an hour. The Kingsford starts to cool down before the chicken is cooked, forcing me to add more. PITA.
I much prefer the Kirkland. Burns longer, produces plenty of heat, but more ash. On that same chicken cook, the same amount of charcoal (two of the Weber baskets, on either side of the bird) easily makes it through the cook time at full heat without replenishment.
When doing long smokes in the WSK, I find Kingsford Pro to be next to useless. The Kirkland isn't as long-burning as, say, B&B, but it will get the job done for 4-6 hour cooks. I break out the B&B when I know I'm looking at 8-10 hours.