We have both on the contact page, and we get more people filling out the form than emailing us, which I guess is surprising but the contact form is right there whereas the email link is a click away.

I really prefer them to fill out the form, because when we can associate their message with their browser, cookie, and IP address, I can get all kinds of useful information eg whether they came from an AdWords link, how many visits to the website they've made, whether they've ever clicked through a newsletter, their IP address (which I can use for geolocation), whether JS is enabled, etc etc.

I also find that it's easier to block spammers via the contact form than the email link, because of all this information I know about them.