I use both- but, why are you going through your cutting mat? I don’t understand why either way would increase wear & tear on your mat. You shouldn’t ever have to press down hard with your cutter- if you need to you need a new blade. My cutting mat - used daily - Lots- has lasted 10 years and counting- some of the lines are worn away. I truly don’t understand why using the mat lines or the ruler lines has any effect on your mat- what am I missing?