Just a few things from my perspective. Before Shinn went SEED, Kira had the upperhand with what I consider to be his newtype abilities, not necessarily pure pilot skill. Part of spacial awareness is knowing exactly where something like a beam is located around you, and where its heading. It would allow Kira to do such a thing as blocking a beam with another beam, or deflecting a shot with his beam saber. After Kira went SEED, he completely 1up-ed Shinn. Shinn even said that if Kira used his chest cannon instead of the rail guns then the fight would already be over, Shinn would most likely be dead and Destiny would definatly not be standing there in one piece. After Shinn went SEED and pulled out the Wings of Light at the same time, he gained the upperhand and simply outclassed SFreedom in speed. I think if it weren't for Kira's skill, SEED, and a bit of newtype abilities, that he wouldn't have kept up at all since as was mentioned before, Shinn was flying all over the place much faster than Kira could comfortably handle.

Overall, if the fight had continued then the only place I could see it going is Kira's defeat or Kira using his newtype abilities more which, as far as the CE AU is concerned, would only put them on even ground.. atleast on Earth. This is void if SFreedom can use its DRAGOONs inside the atmosphere. I think in space, this whole speed issue will be settled since Kira's newtype abilities will allow him to know where Shinn is at all times and then he can just use SEED and the DRAGOONs to figure out where he is most likely to move and then counter by firing at each angle in an attempt to shut down Shinn's insane speed.

A few notes for potential arguments: The newtype ability isn't simply 'activated' such as SEED, its active all the time at various levels. The Shining Finger attack was probably deemed to be way too risky, considering Shinn had no other melee weapons and Kira still had his beam sabers. Even with Destiny's speed, closing in to point blank range on SFreedom/Kira wouldn't be easy, and if he missed or didn't do any heavy damage then he could probably just bend over and kiss his own ass goodbye. I imagine the outcome would be something similar to Saviour vs Freedom.