KSU got the most efficient routes to transport stuff to Mexico and back. UNP is mostly in the US. CNI is Canada and US, takes stuff directly to New Orleans Port - best for transporting grains, raw materials and oil.
These stocks, especially KSU are pricey. However, if the economy picks up, the rails have great operating leverage with little incremental cost. I am wondering when they will start using natural gas for their engines.