Agreed. I did a pure math degree where most of my classes involved copying down 2-3 pages of axioms/proof per lecture, and I settled on mead letter size college ruled spiral notebooks, and yellow note pads for scratch work. Wide ruled led to too much wasted space, graph paper was visually busy and led to awkwardly spaced letters, dot paper just didn't really work. Smaller paper sizes didn't end up holding enough information per page, spiral binding was best for being able to rip out and toss pages, the perforation was nice for the occasional hand in sheet, and I had no need for a nicer quality paper.
Also I always kept Pentel Twist Erase III mechanical pencils with 0.5 mm lead, Hagoromo chalk, and a 4 color set of chunky expo markers in my bag.
Blank paper is too... Blank! And I'm more prone to write big and messy and waste pages (even though it's all digital)...