Digital BW, The Print

While it's possible to get very similar results from using the curves 
dialogue and the levels dialogue, they are not the same and do not 
function the same.

When you pull in the white point slider in the levels dialogue, you 
are clipping all the data above the slider.

If you do not move the end points in the curves dialogue and increase 
the contrast,say, with a traditional "s" curve you are reassigning 
values in the
image but not clipping any.

There is a difference and curves is much less destructive than levels.

That said, the notion that a combed histogram is bad is much too much 
overstated, and generally speaking the problems attributed to them 
arise from
other issues.

J.Z.