Ok, so, aren't we back in the paradox, where depending on the preferred frame we choose, the shower twin is not the same, then?

You're right, he has to accelerate to take off too, that's true. Thank you, I didn't even think of that.

> The paradox itself was not that the twin's experiences are different, rather than the one who traveled more, aged less.

No, sorry. The paradox is the fact that depending on which twin you take as a reference frame, each twin would age more than the other.

Thank you, that is a really usefull answer.

> So the two twins' elapsed times will depend on how fast they are moving with respect to this preferred frame.

In any case (any choosen frame), the one travelling would move faster, right?