I thought I'd be unimpressed by the mirrored version, but I can say that for myself, it really did have a different feel to it.

I've always pictured the boats moving right, sliding down, as if surfing the wave.

The mirrored version makes it clear that, no, they're going against the wave, which makes it that much more of a scary situation!

Now, having noticed that, I see how the position of the rowers in the boat would be enough to deduce that. But still, it goes to show that (at least for me, personally, in this specific case) the mirroring really did bring a more intuitive feel for what the artist was trying to represent.

This is taught in graphic design, how people typically scan information from left to right and top to bottom, in cultures where the written language flows in that direction. However, a counter argument could be made that people perceive paintings differently from the way they read written text. There have been studies about how the Japanese perceive images and sounds with the same area of the brain that processes language, in contrast to other cultures where they're processed separately. [citaion needed]

Look up “spatial agency bias” and “glance curve”

Doesn't strike me as particularly true either.