IMO, with underscores it is not immediate recognizing the elements of an expression like

    some_var.some_fun(some_param, another_param)

Instead with CamelCase, they are immediately visible:

   someVar.someFun(someParam, anotherParam)

But my preferred syntax is Lisp:

   (some-fun some-var some-param another-param)

   (when this-looks-appealing
      (setf you-like-lisp-syntax true)
      (vote-poll 'camel-case-formatting))

IMO, "this-looks-appealing" is more readable than "thisLooskAppealing", but "-" is more space friendly respect "_".