Dotted. Even better than graph paper if you draw a lot of diagrams/figures, in my opinion.
I use Fabriano dotted saddle-stitch as a cheaper and lighter alternative to the Leuchtturm1917, for instance when I'm traveling or at a conference. The paper holds up to any non-calligraphic fountain pen I use.
[1] https://www.eurekalabbook.com/lab-engineering-notebooks/