I did not want to talk in person but could not put my finger on why. I realize that every person picks the mode of communication that he feels is likely to achieve his ends. In the past they have enjoyed either successes or failures using one mode or another and this informs future decisions. So, why did I prefer email with this person but not with most others?
Before getting into that, some other emails issues should be put aside. Email is risky and can lead to pretty embarrassing accidents. I am told that one of my colleagues once inadvertently sent a review of a job applicant's scholarship not to the appointments committee but to most of the people teaching in the area throughout the US. And, it probably is true that people are less inhibited in email but about half the time someone accuses someone else of sending a "flaming email" it is really comparable to walking out of the room and slamming the door or a garden variety personal attack. By that I mean the accusation is just as likely to mean "I have no reasoned response so I'll just say you offended me and mischaracterize what transpired." One other thought on this. Do ever wonder what immediately preceded the "flaming email?" Do you really think it was a polite thoughtful communication of some kind?
And, of course, there are the "no email" people who do not put anything in writing for fear of losing deniability. One of my most interesting experiences with this was a few years ago when a faculty committee was asked to evaluate several faculty members and rank them. The standards to be applied were tenure standards. When the process was over, a disappointed applicant asked to see the written record. There was almost none. Yes, 6 people had ranked at least 6 others including a review of scholarship, teaching, and service and had evidently done so with creating anything but the barest paper record. Email, and writing generally, is not for the gutless.
While some of that influences my own email v. in person choice, I also think it is individualized. For example, everyone has colleagues who, as soon as you begin to speak begin a nodded "no." In other words, before you finish and without knowing what you are going to say, they are preparing a negative response. I email these people when I do not avoid them altogether. I also use email when the person is known to interrupt. It's hard to interrupt when reading an email. The recipient is pretty much forced to hear you out. There is also the matter of quickness. The other day I observed someone in a conversation. She said, "If you will give me a chance to think, I believe I can respond." In other words, some people are just quicker and others need time -- the time it takes to compose an email --to respond.
Finally, and this may seem backwards, people who are naturally conciliatory (I mean really conciliatory as opposed using it as a negotiation tool.) should avoid face to face discussions. To the extent you want to be liked and to seem reasonable, you may regret what you end up agreeing to. Those who prefer face to face are often quit good through their body language and facial expressions at indicating that their opinion of you may hinge on just how agreeable you are. In fact, there is an analogy to informal dispute resolution which often disadvantages the person who just wants to "get along." Those people are better off with more formal means of dispute resolution. Email provides the same distance in person communications.
You may notice a theme here. The characteristic of those I prefer to email are those who feel they can control the conversation so it will turn out to their liking. Email means they lose some of that control. Flip it over and the question is whether the person who emails also just wants to use email in order to control the conversation. Maybe. On the other hand, maybe email is the only way to resist the control the face to face person exerts.
When the parties do not agree on the way to communicate, perhaps there is no communication at all. This favors the status quo and means if you really want change to you to acquiesce to the mode chosen by those in power. Thus, those with power get to set the rules of discourse and they set them to favor themselves.
The face to face people have one really annoying trait. Even though they will not agree to email, if they see you in the hall they are desperate to exchange hello's. But this is a show for observers and simply reflects their need to control even appearances.