What's the standard of choosing primary diagram?

[YuSheng]

Newer one, more details or looks real ?
Just wondering, because some buildings may have a better choice.

[Dylan Leblanc]

Whichever drawing has the most accurate height, most accurate design, and best quality. It changes a lot building to building. Also sometimes better drawings may get bumped from the primary position if they are old and someone has submitted a new drawing which is good and deserves some exposure.