I've been charged with educating my team on "longer or shorter" email campaigns. What is best? Does it matter? Does either help click through and conversion rates?

My research is coming up with there is no right or wrong answer. In either case, it depends on what the goal of the email is, what one is trying to convey, whether or not the email is clean, concise, interesting and of course... the information is valuable and drives a call to action.

So, I'm wondering what the Litmus community thinks. Please let me know your thoughts.