The tone and style you use for your writing samples also depends on the type of writer you want to be or the niche you want to write in.  If your goal is to be a jack-of-all-trades writer, you can benefit from having a number of samples in many different styles and tones. Make sure these are clearly labeled so potential clients can tell the difference between content examples. Or, if you want to continue writing in a particular style that is most comfortable to you, you should only showcase this style in your example content and your writing portfolio.