The language used in the sales letter format should be simple, and suited to your trade. Complicated or complex writing leaves the reader confused and unlikely to read your letter or take action and buy. When a letter writer includes any bonuses, they should be supported with the word "free." For example: "FREE article submission with every SEO article!"
If you want results for your efforts, then what you really need is to understand the most critical aspects of the cover letter. The format is just one aspect. There are more details that you have to take into account. The content is the most essential point you have to bank upon. You might have a very crisp paper with nice format in it but it will not be helpful if you do not indicate the skills and credentials required for a certain job position. Of course, you need to possess the same essential skills, traits and knowledge. Thus, you must evaluate first your qualifications before aiming for the brightest cover letter format.