I'm trying to understand the historical ordering and the practical differences between the Toffoli Gate and the Fredkin Gate.
Where reference  is:
Conservative Logic is then published in 1982 in at least different guises: an article in International Journal of Theoretical Physics and a chapter in Collision-Based Computing.
So the implication to me is that the Fredkin gate precedes the Toffoli Gate.
Given that both gates are universal, what is the purpose of trying to simulate Fredkin gates with Toffoli gates, or vice-versa?
Also, Which gate is more commonly used, and why? A recent Google search finds 84 results for "Fredkin gate" in the Google index, and 86 results for "Toffoli gate." Both of those seem to be dramatic undercounts.