Here is a DallE rendering of the same setup that maybe is less offensive.

How the f**k do we have functional AI that speaks like a human and solves general problems on the level of a university student, but somehow household chores are still done with tech that was invented 50-100 years ago?! Why isn’t there just a hole in my kitchen counter where I can dump dirty dinnerware, pots, pans; the machine sorts it out, washes it, and returns it to the cupboard? Why doesn’t my washing machine sort by color, wash, dry, fold, and stack my clothes? Why do I still have to clean surfaces in my house by manually rubbing a wet sponge at them for hours?

I’ll tell you what I think: inequality. Women did house chores, men invented shit that was fun and useful to them. Maybe as the world moves, hopefully, toward more equality we will find that people who shares their time between chores and inventing stuff will start to actually tackle the problem of simplifying boring chores.

https://youtu.be/jI2zxBAIepI

But, “speedy” relative to what? Relative to the walls of the room your are inside? What if you are in a falling elevator? Relative to the rotating surface of the earth? To the center of the solar system? “Relative to the portal” is the only answer to that question that makes sense.

How can it not be b? Every situation in the Portal games is already exactly like this, but with the portal fixed to a slab that moves with the rotation of the Earth, whereas in the drawing the portal moves as the sum of earth rotation + the movement of the train.

Treating the question seriously, I think it is easy to think the one person is the right choice, because it just seems like less of a mess to deal with. However, I also think the end result is that you will never feel safe in your home again. You will always second guess if every squeak you hear is yet another person who somehow have made it into your house. This is the path towards slowly descending into madness.