The newer trains could use some improvements, to be honest.
The Scout Train is by far the weakest option. Its canister shot feels almost pointless, offering no real reason to choose it over the auto-cannon. While the auto-cannon is somewhat effective against armored enemies, it struggles significantly when dealing with zombies and incoming AT grenades, making it a less versatile choice.
The Heavy Assault Train is decent but still falls short compared to the default train. While its special ability and armament can make it enjoyable to use, the default train’s healing ability gives it a clear edge in terms of survivability. This makes the Heavy Assault Train feel like a less practical option for prolonged engagements.