david weaver
Just how much work it is to hand sand a board and remove every single mark that you can see, even when there are otherwise no surface defects.

The plane wins hands down and then some, even if the surfaces look the same.

The difference is subtle, I think. When the lighter side is planes, it's more figured than the other. When the other side is planed, they look similar in figure.

The figure also looks more colorful and less like a blotch on the planed side.