The enn comes from the religion of demonolatry. The song was given to EA directly by Belial himself for the Lake of Fire ritual (as explicated in the Book of Azazel) in his role as a Gatekeeper.
As far as I know, he does not have a preference and responds to both. However, the song has a distinctly different energetic flavour to it than the enn. I personally don’t like the demonolatry enns, and never use them in my practice, but I love chanting Belial’s song. It just has a better resonance for me.
I have used EA’s Conjuration to Summon Forth for a variety of different spirits. It works, though when a member here on the forum used it to call the archangel Michael, the angel was none to pleased and asked why he was summoned with “that demon shit.” lol
You need to stop asking so many questions and start experimenting for yourself. We can all tell you our personal preferences as to what to chant (or what the spirit prefers, according to our own experiences) but, in the end, they are just our preferences. You will never get everything perfect, and you have already been provided with all the information you need to make an attempt to summon a spirit, so you should stop going around in circles and start to put things into practice.