Suppose you have a new boss and your former boss was a vicious and dictator one. Now you are visiting the new boss for the first time. He seems to be a nice person to you, but one of your colleagues who has worked with him before, after hearing your opinion about the new boss, would reply mockingly or sarcastically:
"Don't be fooled by his appearance! he is not better than the former boss, actually they are both as bad as each other!".
We Iranians have a proverb that implies "none of these two people is better than the other, both of them are bad/evil/vicious". it literally says:
"The yellow dog is the jackal's brother."
Its etymology is like this:
Once there was a mischievous jackal living in a village, he annoyed people so much that they expelled him from there. But he entered again, in disguise and as a yellow dog. Since people had a good opinion about dogs accepted him and called him "the Jackal's brother" (because he looked like the jackal). This time the jackal continued his vicious actions in secret so the people couldn't find out the truth; but in a rainy day, the yellow color was washed off the jackal's body and the people found out the truth, so they said "Oh, look! the yellow dog or 'the jackal's brother' is the jackal himself!".
Is there any idiom, expression or proverb than can be used for comparing two bad, vicious or evil people that would imply "but this one is not less vicious than the other, both of them are bad"?
I have found "They are two of a kind". Can I use it as an equivalent for that Persian proverb (with a negative connotation)?
In this proverb, "the yellow dog" is the symbol for a bad person, and "the jackal" is the symbol for a worse one. Although one of them seems better than the other, in practice both of them are horrible and act vicious. So to the people, there is no difference between them in practice.
We use this proverb when comparing two vicous or bad politicians too. For example, if the new president fails to fulfill what he had promised in his campaigns about improving the situation of human rights and freedom of speech, and just acts like the former tyrant president, then unhappy people would say:
It is clear that this one isn't different with that former president. Actually, they are as bad as each other, as the proverb goes "the yellow dog is the jackal's brother", so we shouldn't be optimistic about any improvements in the human rights in the country in this person's presidency either.
Here are two other examples, that @Josh61 has found in some websites, and a literal translation of that proverb is used in those papers: