Which of the following is an effective thesis statement for a compare and contrast essay?

I believe orcas are more interesting than dolphins because they are known as killer whales.
Orcas and dolphins are members of the same taxonomical family due to some physical similarities, but they have many behavioral differences.
Orcas are called killer whales but are actually members of the dolphin family for a number of reasons.
Orcas and dolphins are alike and different. They are alike because of some physical similarities. They are different because of their behaviors.