It's impossible to get a completely accurate comparison in the case of some pictures, especially ones involving multiple characters or split second timing. And yeah, the animations in some cases are noticeably different, even if the move is the same. If it's a case of them not facing the screen in Brawl though, when they are facing to the left, I simply take a picture of them facing right, and flip it in Photoshop, to make it look more like it is in Smash 4.
Also, while it's probably a bit early to be doing this, as we haven't got all of the characters out of the way:
Would it be possible for anyone to get a good screenshot of that same area of Skyloft within Skyward Sword? I want to compare original Skyloft to both the Project M version and the Smash 4 version. A first person screenshot would be preferable, assuming Skyward Sword has a first person look-around mode like most 3D Zelda games.
I'd do it myself, but Brawl is pretty much the only Wii game I can run well in Dolphin and is really the only one I'd ever want to run anyway. And I would take an photo with a camera from my Wii, as I do have Skyward Sword on my softmodded Wii, but I haven't played Skyward Sword myself yet and it'd probably take me a bit to find that place. Plus I don't have easy access to my Wii right now.