兽面人心比人面兽心强百倍
[shòu miàn rén xīn bĭ rén miàn shòu xīn qiáng băi bèi]
This translates to 'A beastly face but a human heart is much better than a human face with a beastly heart'. It suggests that someone who looks rough but has a good heart is preferable to someone who looks pleasant but behaves maliciously.