This statement is total bullshit. Weather Underground doesn't have better data or coverage than the Weather Channel. If you're really looking for more coverage, check out the weather blogs.
It's still sad though. Weather.com doesn't have anything that works as well as the WunderMap, and certainly nothing I can leave running 24/7 in a browser unless I want to restart it every few hours.
The real skill in weather seems to be from WeatherBill, now The Climate Corporation:
http://ecorner.stanford.edu/author/david_friedberg
When there is big money on the accuracy of the weather prediction and measurement, they tend to get it right.