As many said before: Both. I do both PL and 12x12 spreads happily.
I started "scrapbooking" (instead of only glueing fotos in albums without a "plan") when in Dec. 2013 I was done with catching up 7 years worth of fotos from may wedding and the firstborn on and was looking a nicer way to handle my fotos.
After 2-3 months of figuring out what I liked I settled into mixing PL spreads with different types of PageProts alternating with 12x12 LOs. For the years 2008/09, 2010/11, 2012/13 where I already had the fotos and memories in albums I decided to reprint the fotos as 2x2 or 2x3 and make some overview pages that go into the one 3-ring-binder I currently own. Starting with a beautiful LO about my wedding, overview pages from 2008-2013 I thus arrived in 2014 an do PL monthly since then, still mixing in 12x12 pages. I came to an average of 3-6 pages per months (i.e. 2-3 spreads), I always just try to complete a page when laying out my fotos in (more or less) chronological order.
The 3-ring-binder gives me enough flexibility to go back and file LOs with old fotos I want to highlight (I had 2 post-bound albums first, ugh, this drove me crazy, as you have to juggle your LOs out of the protectors instead of just moving the whole thing around. Grrr).
I do understand that after a while (several months/years) there will be a problem with sorting chronologically into multiple albums, but then I probably will not go back as often to fill gaps with dedicated LOs for older fotos.
I love the effect and surprise everyone expresses when flipping through this binder as every page is different.
And the first thing that attracted me to scrapbooking was PL, I kind of grew into LOs only along the way, taking challenges in another forum as inspiration to create 2 LOs per week.