My favorite butt combination is the Jamisons' "Renowned Mr. Brown" * ("Southern Succor") recipe, which is notoriously heavy on black and cayenne pepper (yumm), and the accompanying "Southern Sop" that adds vinegar and still more pepper to the unused rub.
Out of a sense of experimentation (and laziness) I've tried Mr. Brown without the mop. It's not as tasty. I've tried many other rubs, mopped and not, and so far nothing else measures up for me.
So I guess it's a question of what you're looking for and what does it for you. When I want pulled pork that really wows, I use the most flavorful recipe and I mop.
--John
(When I'm feeling lazy, like in 'just put it on the cooker and wait for it', WRB is my choice. Sometimes I use WRB and mop with Scott's. Not the same, but good.)
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* Cheryl and Bill Jamison, Smoke & Spice, p. 53.