In this Harvard Business Review article it concludes that people are more likely to have a meeting with you, if you ask face-to-face rather than email.
I'm sorry but don't we know this already?
If I walk up to a stranger in the street, and I look engaging etc, they are more likely to say yes to having a coffee. If I do this over email, you will probably do want I do with a lot of the email I get, just delete it.
So how do I get that face-to-face impact while on-line? Well you could have a personal brand? You could decide not to write like everybody else? You could try and not try and sell to me the moment you meet me? Yes, I know that's all a bit, dur. So why not make a change, it is after all Christmas?
Despite the reach of email, asking in person is the significantly more effective approach; you need to ask six people in person to equal the power of a 200-recipient email blast. Still, most people tend to think the email ask will be more effective.