The Chameleon Copywriter

In his book Effective Email Marketing, Herschell Gordon Lewis gives a “dangerous” general rule about email marketing. He says it’s dangerous because stating that something is a general rule opens up one to criticism. But here goes:

Text tends to outpull HTML when your message suggests urgency. HTML tends to outpull text when your message suggests [...]

I enjoyed this email from the Col. Littleton catalog.
It would not have had that same impact as a plain text email. Do you agree?
I’m not usually impressed with the HTML emails from large companies because, as a copywriter, I’m interested in studying the copy and the copy in these emails is usually very lacking.
But [...]