Know-How Exchange : Research/Metrics

I'm working with a small B2B high-value service company, with a very focused vertical. They are considering several options for growing business within that vertical:

* letter with "cold" call follow ups
* webinars
* networking (big presence at local and national events)
* partnering with a national media outlet to create a
* electronic newsletter for the vertical.
* white papers

ROI on cold call campaigns isn't hard to find, and seems pretty low - though people seem more comfortable "banking" on it than anything else.

What's the conventional wisdom for everything else? Are there stats somewhere on what kind of results you can expect from these other forms of lead generation?