I'm a 0.5mm, maybe 0.7mm, person myself. I've always liked the fine line and ability to write details. Probably comes from all the math I did going through school.
If I'm doing rougher marking then I just use a regular pencil.
I too use the Pentel however mine is Super Hi Polymer 2B size 9. It seems I'm always adding more lead since it's so soft. It's a trade off because I love how it writes. The issue too is the standard lead that comes in the 209 pencil is so hard, it's light and neither my wife or I can read it. I see Pentel makes five hardness types for the 9mm and as shown in the attachment the harder the lead, the lighter the writing. http://davesmechanicalpencils.blogs...nd 0.7mm,manufacturers offer far fewer grades.
It seems no matter what you make, a whole new world of information and options open up.