Marktest is leading in Top 10K Sites and Top 100K Sites.
Observer has better usage coverage in more websites categories. Including Computer & Electronics, Arts & Entertainment, Business & Industry, Software and 12 other categories.
Marktest is leading in News & Media, Newspapers, Music & Audio and TV & Video.
Observer is leading in most countries, including Russia, Spain, United States, Algeria and 9 other countries.
Marktest is leading in Italy, Portugal and Brazil.