Artists are always asking each other "so what did you use to make that line ?" Lines always seem to look better on someone else's work. The truth is that oftentimes we are admiring the work of an experienced artist who has developed a certain degree of confidence in their line making. Don't get me wrong, product does indeed matter and I of course have my favorite fine-liner and heavy liner pens and products, but the key to making line and marks is practice not product. Once you have mastered the ease at drawing or scribbling a variety of lines you are probably ready to obsess over the "blackness" of these lines....that is another conversation.