What villain ties their victims to train tracks anymore?
The questions are flawed. The situations are filler that just makes it harder to consider. In the first, it wouldn't occur to me that pushing someone into the path of a train might stop it to prevent more deaths (and if I knew that, I'd either be a demigod and use my powers to save all six, or a huge nerd and would be in a lab doing science in the first place). In the second, if the train is going slowly enough that it wouldn't derail on a turn that tight, I would think you'd have time to flip the switch and save the one person in its path, especially going by how close the figure at the switch is to the single one on the track. In both, if the train is going slowly enough that one overweight person could stop it in its tracks or it could make that turn safely, who the hell is driving it that wants these palookas dead, and why did he choose such a boring weapon to do the deed?
If I point all this out, you respond "The question is about whether five dead people or one is worse," and I answer "five are worse" but that doesn't necessarily mean it would apply to my actions in the situations. And you can't really ask the question with bare-bones details, either, because neither would be a bare-bones scenario in real life.