I dont know why it took me until now to notice, but how are they pulling off the same weight across the platform?

Logically I figured if you added in room for an extra passenger or so with more room equaling more material, ........... well you get the point. What simplistic thing am I missing?

Secondly, I was informed about the performance likenesses between the two, and that there was a thread about this. Any clue what thread that is?