The "ranking" in the vote is the same as the price. I get all that. Pulled the trigger on the 300 after seriously considering the Tammy. But, at the time, was going through a series of wildlife shots taken with my 100-400 (while watching some Verdins build a nest outside of my window) and was disappointed with so many of them that I felt the Tamron would not be a better option (at least in the under 400 mm range) than what I have. That and the temporary price that was being offered through the buyer's group on www.canonpricewatch.com
was all I needed to push me over the edge. I know what the 300 can do since I rented one last fall. I understand that a zoom can be handy at times vs. a fixed length and the use of TC's. The price difference is significant.
Had I not been seeing so many not-too-sharp images (most of which are probably my fault and not the fault of the lens) at the time, might have still gone with the Tammy. But, I will probably sell the 100-400 soon then look for a good deal on the 2xTC.
BTW, never underestimate the power of a chimney, and a famous one indeed!