The journal Nature just released a study comparing it to Britannica. The investigators peer-reviewed science articles from the two sources:
The exercise revealed numerous errors in both encyclopaedias, but among 42 entries tested, the difference in accuracy was not particularly great: the average science entry in Wikipedia contained around four inaccuracies; Britannica, about three ...
Of a total of 42 comparison reviews:
Only eight serious errors, such as misinterpretations of important concepts, were detected in the pairs of articles reviewed, four from each encyclopaedia. But reviewers also found many factual errors, omissions or misleading statements: 162 and 123 in Wikipedia and Britannica, respectively.
They don't say, but I expect the quality of writing was better, and more consistent, in Britannica.
No mention of whether telephony was one of the subjects reviewed.