Hmmm, I'm not sure - I think it could go either way. A designed email could look professional, but it could also look as though it is a mass email sent to lots of people and reduce the chances of people taking much notice of it.
Depending on what your field is, I think I'd be more inclined to take the personal approach and have it linking to a professional looking website.
Also beware things that might identify your message as spam and filter it into junk folders - e.g. sending 1 email to a mass list of people, having certain words in the subject line etc.