You're right, the flame graphs (which is really an adjacency diagram with an inverted icicle layout) doesn't exaggerate subdirectories like a sunburst layout does. I wrote about problems with the sunburst layout before in ACMQ[1]:
> The sunburst layout is equivalent to the icicle layout as used by flame graphs, but it uses polar coordinates.7 While this can generate interesting shapes, there are some difficulties: function names are harder to draw and read from sunburst slices than they are in the rectangular flame-graph boxes. Also, comparing two functions becomes a matter of comparing two angles rather than two line lengths, which has been evaluated as a more difficult perceptual task.10
(I should have mentioned that they visually exaggerate deeper slices, too). I think they are pretty, but, more difficult to read.
The other app has a pie chart and trees. Both can't visually show everything at once, all subdirectories.
I agree with that criticism with respect to profiling, but for filesystems I find the increased surfaces of the outer rings makes the evaluation easier as the filesystem reaches smaller amounts of data, especially as FS tend to be relatively shallow in POI terms.
The problem is that humans are not very good at comparing angles, which is one of the reasons why pie and donut charts aren't good (and sunburst is kinda like a donut, so the same criticism applies).
> The sunburst layout is equivalent to the icicle layout as used by flame graphs, but it uses polar coordinates.7 While this can generate interesting shapes, there are some difficulties: function names are harder to draw and read from sunburst slices than they are in the rectangular flame-graph boxes. Also, comparing two functions becomes a matter of comparing two angles rather than two line lengths, which has been evaluated as a more difficult perceptual task.10
(I should have mentioned that they visually exaggerate deeper slices, too). I think they are pretty, but, more difficult to read.
The other app has a pie chart and trees. Both can't visually show everything at once, all subdirectories.
[1] http://queue.acm.org/detail.cfm?id=2927301