writes "Nature magazine recently conducted a head-to-head competition between Wikipedia and Britannica, having experts compare 42 science-related articles. The result was that Wikipedia had about 4 errors per article, while Britannica had about 3. However, a pair of endevouring Wikipedians dug a little deeper and discovered that the Wikipedia articles in the sample were, on average, 2.6 times longer than Britannica's - meaning Wikipedia has an error rate far less than Britannica's."
Interesting, considering some past claims
. Story available on the BBC