Electric traction is highly capital intensive, steam traction is highly labour intensive and requires [say] three hours to get a head of steam.  Diesel traction is lowish capital cost and available at the throw of a switch.  You choose.

Electric traction is highly capital intensive, steam traction is highly labour intensive and requires [say] three hours to get a head of steam.  Diesel traction is lowish capital cost and available at the throw of a switch.  You choose.