Skier88 - 4:28 pm on Oct 25, 2011 (gmt 0)
The difference is that word-wrap sets what happens when a word can't fit inside its container, and word-break sets which characters are treated as word seperators (normally that's only space characters). In the example the url can fit inside the container by jumping down below the image, and word-wrap will sooner move it than break it. What we want is for it to not every try to fit - to treat every character like a space. And that's what word-break does.
On a side note, I think a combination of Fotiman's first and last comments is a better breaking strategy than either method. That is: keep all the text to a column on the right, but use word-wrap so urls try to stay unbroken and you're cross-browser compatible. That way the URL doesn't go below the image, but you also avoid stupid breaks where you've only got a few characters on the first line.