The difference between beasts and human godclads that beasts were born with divine flesh. The number and size of the divine flesh indicate the upper limit and the power of the beasts, respectively.
A beast with six types of divine flesh or organs will only be able to reach rank 6. But the bigger the divine flesh or divine organ they have, the more powerful they will be at each stage.
The number and size of divine flesh can be likened to the potential and power of a beast. Since immediate power is oftentimes more important than future potential, the beasts with a larger size of divine flesh tend to survive more regardless of the amount of divine flesh that they have.
This makes it so that beasts that reach a higher rank tend to have larger divine flesh and are bigger in size than their counterparts. This was why it was easy to identify the four rank 6 beasts in the beast tide.
