If I can see the person online in messenger with idle or available status, then I use IM. Otherwise, I use emails.
depend, what is your primary purpose,.....on email you can say anything that you wanna say for the single page without any disturbing "incoming message that you receive via messanging"
Actually it depends what type of communication i need! If there is no difference which one to use than I prefer IM over e-mails, because it is faster and u can add your thoughts any time!
It depends on the person with whom I am trying to communicate. If the person lives online, then obviously IM is better... otherwise e-mail is the preferred choice! Regards, RightMan