I usually use Yahoo. But after some looking into other services like hotmail and gmail. I noticed that they have something quite useful.
It is linking acounts./ automatic forwarding. (Used if you want to check all your mail from multiple accounts in one.) And you can even select an email address for the From field when you compose a message.
Anyway, one reason for having multiple accounts is like say, suppose you sign up twice for an email-based login at some website. (Or if you get banned and have to sign up again.) This way, you won't have to change your primary address if you don't want to, and instead, use email forwarding/etc.
So, which email service do you think is the best to use as the primary right now?