I think it's 6:4, Ragna just can't run and hit everything like he wants to, he just has to be patient, and learn to block Arakune's terrible and slow mixups. If Ragna IBs Arakune's jb, then Arakune is at a hard disadvantage, ID can beat any follow up at that point, and I've even eaten a 5B after hitting Ragna with my jb, the truth of the matter is that jb is good for fake pressure, it's a terrible and unstable combo tool. jb only beat's 6a if Ragna poorly times it. It never beats ID on the grounds that ID at least has invincibility. Arakune lacks a solid way out of pressure. The best he can do is mash backdash, chick block, or just barrier you off of him. With meter the best he can do is either CA or IB > Super.
On the flip side if Ragna chick blocks, Arakune has a terrible time getting in. And being forced to respect ID, we're not going to be too hasty.
Thing is, once Arakune catches Ragna slipping, thats 5-6k. Arakune can also zone Ragna pretty damn hard, in and out of curse.
It's not 3:7 to me, because 3:7 says to me "you have to rely on your opponent's screw ups to win", where as 4:6 says, "you must out play your opponent to win", and that definitely looks like the case for Ragna vs Arakune.
http://www.youtube.com/watch?v=uqKnaB7MsQM