An advanced steam train can be fueled with a variety of simple fuels. A diesel train requires complex fuel. An oil refinery must guarantee the availability of kerosene.

A diesel train has a higher maximum speed. But because a steam train has higher acceleration, it is even faster over medium distances! A diesel train cannot reach its maximum speed.

EM trains have many disadvantages:
1. Insane amount of energy. I placed 1 charger, it covers only 5% of my base on city blocks. And it consumes 250 MW. This means that the entire base will require 20 chargers. And that's 5 GW (!) of energy. My nuclear power plants generate 1.8 GW. I placed a charger on a straight road that leads to the mine - 150 MW. This is absurd.
2. The chargers have an inconvenient coverage area. It is circular. This will result in many areas with overlapping coverage. And that means even more chargers, which will make the layout of my base even more inconvenient. It is inconvenient to track the coverage area, as it is not displayed on the map. It would be much better if one charger were required for all rails. Or at least if the coverage area were square.
3. Chargers need to be placed along the entire route to distant mines. They will have to be protected from biters.

I unlocked EM train technology. However, I decided to stick with steam trains. (I only replaced the freight cars with more spacious ones.)