This breakdown ignores the rock/paper/scissors nature of artillery/infantry/cavalry, and also ignores the fact that you can only support so many troops in a base (so once you hit your limit, it's worth buying less cost-efficient troops that are more food-efficient).
In the short game, though, I was a little surprised given the caveats above how stand-out the choices were. If you want to build offense quickly, bikers are the way to go. If you want to build defense quickly, gunners or knockers are equivalent (with gunners being half-again more costly).
If you're strapped for resources, then your best offense is scouts, while your best defense is knockers.
This is a pretty superficial inspection of the data. What would you get out of it? Any thoughts on how to best divide the separate "artillery", "infantry", "cavalry" overlap for both offense and defense?