I prefer email because it can avoid much of the "he said/she said" and skip right to, "Here's the email." Occasionally, I've sent off the, "Per our conversation, I have..." email. I'm obviously documenting what happened and sometimes that's necessary. CYA and such.
I've always been good about checking my email and replying in a timely fashion. A phone call, for me, are for those things that demand immediate attention and unless you're my supervisor you can't dictate my priorities for the day. Send an email and when it's done or there's been a change, I'll reply.
I would guess part of it is generational, with younger people leaning more toward email.