I realize this is anecdotal and mostly unscientific, but I started using Pennzoil back in '87 when I had a huge POS Ford Escort with the simply-awful 1.6 liter. I had been using Havoline because it was inexpensive (and I was poor), and the POS was burning oil like crazy...in desperation, I tried Pennzoil and it stopped using oil...almost completely. I didn't know squat about oil back then, all I knew was it burned Havoline and it didn't burn Pennzoil.
So I started using Pennzoil from that day forward and never (repeat: NEVER) had a car that ever burned any measureable amount of oil. Now I know a lot has changed in the last 20 years, and I know that Havoline is an excellent dino and well-loved on this forum. And maybe I was just lucky, but I swore by Pennzoil, and if I was going to use a straight dino, that's probably what I'd still use. And I've always been a little gun-shy about Havoline after that experience, even though I know it's almost certainly unfounded now. It just left a bad taste in my mouth (figuratively speaking, of course).
But now, since I'm so "knowledgeable" (cough, cough) about pcmo's, I'm using MC 5W-20 Syn Blend for the same or less $$ than Pennzoil. Will it prove to serve me as well as Pennzoil has? I hope so...hopefully even better?
And as for all the marketing/Slick 50 mumbo-jumbo, I couldn't give two flips less about it. I'm only concerned with how good the motor oil is...nothing else.