Amazon Webstore is leading in Top 10K Sites, Top 100K Sites and Top 1M Sites.
Ubercart has better usage coverage in more websites categories. Including Business & Industry, Shopping, Arts & Entertainment, People & Society and 218 other categories.
Amazon Webstore is leading in General Merchandise.
Ubercart is leading in most countries, including United States, Russia, Ukraine, France and 140 other countries.
Amazon Webstore hasn't got a lead over Ubercart in any country.