My idea is that J1c3 can be associated with the development of various Semitic languages as it is older and more widespread, I think J1c3 people were dispersed throughout the Middle East before large scale war became the norm. My guess is that the people associated with J1c3d made their own Semitic language dominant through large scale conquests quite some time after other Semitic languages had developed. So my choice for proto-semitic would naturally be the oldest of the two J's (J1c3). I think E1b1b1c1 belonged to a language group which was replaced by Semitic long long ago.