Thinking about it…I am pretty sure that homeworld actually does work off of a height based merit system.

Admittedly, it makes a lot more sense. Being taller is an indication of having more power for gems. Ruby and sapphire seem rather weak on their own, but together they are the tallest and strongest member of the team. Rose was the leader, as well as the tallest. Jasper has been the largest individual threat on the show, and she is tallest. When gems fuse, they generally grow largers…

I suppose the fact that size adn power correlate because gems bodies are not fixed, but a manifestation of their power… more power means more power to work with.

So…yeah…yellow diamond is probably super tall.