wireless networking - Is it better to choose a more-crowded WiFi channel or one with a strong competitor?

In this other SuperUser question, the consensus was to stick with WiFi channels 1, 6, or 11.

But what if two of those channels (channels 1 and 6, for example) are both very crowded, but the other channel (channel 11, in this example) is much less crowded, yet has a very strong competing signal?

In that case, is it better to use channel 1 (or 6) or channel 11?