Seats half full or half empty

Kevin Drum shows the following graphic (link) to illustrate where the House stood on authorizing force in Syria.

What interests me is whether the semi-circle concept adds to the chart. It evokes the physical appearance of a chamber, presumably where such a debate has taken place -- although most televised hearings tend to exhibit lots of empty seats.

The half-filled circles in particular do not make peace with me.

Here is a tree map of the same data.

Notice that legend boxes are unnecessary.

A pie chart with appropriate labeling acts similarly.

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A profile chart produces mixed results:

This version has the advantage of stacking the voting variable. It doesn't do a good job describing future scenarios.