E-mail. You have time to think about your answers, you're not dealing with a call at an inconvenient time.
I hate talking on the phone. Always have. I'm just not much for small talk and I hate when people go on and on. I feel guilty when I say "I have to go now. Can we talk more later?" I'm not a big conversationalist and I have a couple of people who say "Are you there?" if I don't respond right away, if I'm trying to think about my response before I speak. Drives me batty.
I have friends that are very nice people but they are lonesome and seem to have a lot of free time that I don't have and they call all the time to talk about TV shows and the like. Not to mention the one "friend" who always calls asking for favors.
If it's an emergency or a friend who really needs to talk, it's different.
E-mail was a big help when I was a team mom.