Make sure you choose a cover letter format that you feel most comfortable with. It should be something that could best express your personality but keeping it as formal as possible. Be wary of the details of the cover letter format. It must be clean and neat. It should provide the data directly. There is no need to be colorful or playful with the fonts.
Your cover letter format is very important to your success. With a high quality motivation letter, your chances at getting an interview will dramatically increase. Don't take shortcuts. Pay attention to both what you say (content) and how you say it (format). Your efforts will pay off in your career success!