This is cool, and it showed me something that I should've noticed a long time ago but only just now did.
For all their weaknesses, pie charts are much better at showing what percent of the total a combination of options makes up. At a glance, you can tell on the SICP pie chart that about 50% of people have never looked at it and about 50% have read at least some of it. This is not at all obvious from the bar chart.
For combinations that happen to end up adjacent to one another in the pie chart. For other combinations, it's not really any more obvious than in the bar chart.
Perhaps pie charts would be less sucky if they were interactive and allowed you to rearrange and/or re-colour the slices. Then at least you could go looking for subsets that add up to 50% of the pie (or 31.42%, or 99.94%, or whatever). Though I can't help thinking that there are better ways to do that.
For all their weaknesses, pie charts are much better at showing what percent of the total a combination of options makes up. At a glance, you can tell on the SICP pie chart that about 50% of people have never looked at it and about 50% have read at least some of it. This is not at all obvious from the bar chart.