I think the feather you pointed out was actually the one that caught my eye. It's hard to see the difference, but that was the one I was staring at the most.
Nice how you presented the level view, that really shows the symmetry. I think some of my perception was from the camera angle. With the angled view, the far wing looks quite natural. With the close wing, it looks a bit flatter towards the camera, and the 4 or 5 feathers on the end look a bit dagger like. Almost like there is a slightly mismatch in depth between the geometry (seems 2D) and the texture (appears 3D, with a slight curve, like roof tiles), but only visible from an angle where they don't align, and from a distance close enough to see the detail. Oh, and maybe that's it. The texture looks a bit blurred close to the camera, like it's not high enough resolution to be sharp and detailed at that distance.
Regardless, it's still a very convincing wing. No need to obsess over it. You've already well surpassed the "good enough" stage.
I rather like the detail in the new version, especially the short feathers on top near the front edge of the wing.