.3 mm mechanical(drafting) pencils have been a personal favorite for 30 years, since i filled data on tiny lines in manila folders.
fat lines are gross. i still write so tiny that most folks can't read it.
skinny leads have to be pretty soft, because the hard ones break. writing with .3 mm leads simultaneously requires a delicate and firm even touch.
we all have things we wont compromise; i refuse to write with fat leads.
seen a cab lately???