This is a “loaded” topic to say the least. There is simply no easy answer. HTML e-mails have higher read and clickthrough rates. But that is based on the industry as a whole, and not the desire of each individual user. Personally, I prefer text-based e-mail with a link to the HTML version. But others prefer the opposite. So I suggest you give your subscribers as much control as possible to determine how they want to receive your e-mails. A few points to consider:

• Always offer subscribers a text-based version of your e-mail.
• For text-based e-mails offer a link to a Web-based version they can easily access.
• On your Web site sign-up page give them the option to choose either HTML or text.
• On your website, provide samples of your HTML e-mails so people can judge for themselves if it’s something they want to receive.
• Consider every design element before using it. Just cause you are using an HTML-based e-mail doesn’t mean you have to add visuals. If the design elements don’t help you communicate more effectively then don’t use them.

So what I am saying is give your subscribers as many choices as possible and let them decide.