School assignment Nothing? 🙂
They are both strong, steadfast women, but so are all women in tanach. They are both also both know for their tzniyus. To contrast – Ruth was a giyores so her strength was a personal choice as opposed to ingrained in her upbringing. Esther was also placed in a position where she had to breach her concept of tzinyus and apporach the king while Ruth was never put into the spotlight like that.