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First, I disagree. There is plenty of detail in those shots. Second, if you want to make a point about the Canon and Sigma respective bokeh, the only valid way to do it is a controlled comparison with the same subject matter. That site has done it. You have not.
Anyone can cherry pick examples of ugly bokeh for any lens. Your samples are invalid.
That's the last thing I have to say about this.
+1 Absolutely. Anyone who has any scientific background, or experience, knows how easy it is to fool yourself and/or others when the results of comparisons are not controlled - i.e. same subject, same lighting etc...