Marktest is leading in Top 10K Sites and Top 100K Sites.
Observer has better usage coverage in more websites categories. Including Business & Industry, Arts & Entertainment, Computer & Electronics, People & Society and 24 other categories.
Marktest is leading in Music & Audio, Soccer and Religion & Spirituality.
Observer is leading in most countries, including United States, Russia, Japan, Germany and 7 other countries.
Marktest is leading in Brazil and Portugal.