Observer
2 websites

Observer is free to use

http://observerapp.com/

Observer is a web analytic tool developed by Ludwig Pettersson. Observer also includes a toolbar that lets you view your analytics no matter what site you are on.

VS

w3roi
5 websites

w3roi offers both free and paid options

http://www.improvely.com/

Track & Improve Your Online Marketing Results. Track ad clicks, organic & search traffic, signups and sales. Monitor your ads for click fraud and easily run A/ B ...

Market Share by Top Websites

2 In terms of market share, Observer is clearly lagging behind, losing to w3roi in all segments.

Websites Categories

1 w3roi has better usage coverage in more websites categories. Including Adult and Business & Consumer Services.

2 Observer hasn't got a lead over w3roi in any websites category.

Geography

1 w3roi is leading in most countries, including United States, Mexico and United Kingdom.

2 Observer is leading in Russia.