Colouring pens vs colouring pencils?

Got my first adult colouring book which I'm so excited for, I've been wanting to get one for so long! However I have a problem, I've no idea if I should use colouring pens or pencils? I like pencils better because they don't layer unevenly if you go over the same area multiple times unlike pens, but pens are more pigmented. Help? 😂