Phones are definately better because you usually get an awnser pretty quick.
I'm all about well timed speed when it comes to contacting a girl for the first time. And when I do I want to know what's going to happen right then. Even if you leave a voicemail, the girl's more likely to get to you faster then if you write an email.
I personally don't check my email any more then twice a day, but my cell phone is on twenty four seven so I'm always acessible that way, like millons of other people in the country.
Plus I think calling is a more direct way of showing interest. There's way less emotion and ways to manipulate the situation in even a well written email. But you can deliver a clear message that you can alter on the fly on the phone.
Just seems to me like the advantages of direct contact for just one person, are far more beneficial and numerous for calling.