Marktest is leading in Top 10K Sites and Top 100K Sites.
Observer has better usage coverage in more websites categories. Including Computer & Electronics, People & Society, Software, Business & Industry and 10 other categories.
Marktest is leading in TV & Video, Music & Audio, Newspapers and News & Media.
Observer is leading in most countries, including Russia, United States, United Kingdom, Germany and 2 other countries.
Marktest is leading in Brazil, Portugal and Morocco.