When meeting new people the standard is to exchange business cards. If I’m doing this with someone who is selling to me I am not very strict about keeping track of the card and I’m not motivated to poke at my phone or type on my computer all of that data entry.
If you are selling you want your prospects to get and keep your information. So make it easy for them. Lifehacker shares a tip on how to create an email that will auto enter this data into the standard address books (Apple, GMail, Outlook). I recommend only having one attachment with the vCard because it works on all 3 and why make it harder for them to read and choose.
While we’re talking about digital business cards read my older post on the matter.