Just a note, from having worked in a Congressional office that phones are usually answered by interns and a staff assistant, mail is opened almost exclusively by the staff assistant, but this is still the lowest level position in an office so the marginal difference is pretty minimal. And for any issue that's time sensitive, don't bother physically mailing because it has to go through extensive security checks before it gets delivered to us. I'd say the ideal way to maximize impact with an elected official here is to ask them the question publicly (FB, at a town hall) and try to garner as much support as you can so they feel like they have to answer you positively.
You're correct in phone calls and letters counting way more than e-mails or online comments. Especially if the comment is thoughtful. If the issue is hot button, it won't do anything. But for marginal issues like these, a couple calls can easily swing votes.
