I'm not too picky but I like a fine-point nib. Medium I find I write more untidily. But fine-point tend to get clogged too easily and the pen is unusable when there's still stacks of ink! I also like pens that are really fat. But mostly I use a mechanical pencil; after I did a stack of marking this year with it I got hooked on the smooth thin rub-outiness of it
