I'm curious like a cat and want to know more about the Sport vs. Fastlane in terms of handling/geometry characteristics, than the website supplies. I know they have the geometry measurement specs on the site, but I don't really know how to interpret those numbers. One of my current rides is an old Fuji Royale, so if you know anything about that in addition to the two fore-mentioned Gunnar bikes, it would be a good reference point.
It seems to me it would primarily be a question of disk vs caliper brakes. Beyond that, the Fastlane will have a more aggressive, stretched out riding position. Note the shorter headtube and longer top tube lengths. I have a Sport and it is a comfortable, stable bike.
they should more or less ride the same, geometry wise. The fast lane comes with thicker tubing, so it will be heavier, stiffer and it is meant to be used with disc brakes. Basically the sport is what you want if you want a comfortable road bike that can handle light touring. The fastlane would be better for commuting/med touring.
I have a Gunnar Grand tour being built right now. I love the brand.