Percentiles allows you to ignore a few extreme elevations.  If you pick the 1% and 99%, the top and bottom 1% will plot with the same color.  This works when you have a skewed distribution with long tails.

If you clip colors, all those above/below the limits will be show in a particular color.

Stretching

• None
• Percentiles--equivalent to a histogram equalization.  All colors should appear with the same frequency.
• Standard deviation--no difference from no stretch, but the legend will be in terms of the mean elevation at 0 and standard deviations away from it