If you mean compared to an online service, they usually have to restrict how many sites you crawl, how often you can crawl and will have trouble with local and

If you mean compared to an online service, they usually have to restrict how many sites you crawl, how often you can crawl and will have trouble with local and private sites. Google Webmaster Tools can take days to give you updates on issues for example and you have to push your changes live to get feedback. So as a Chrome extension, you can crawl your local development sites, staging sites, sites on private networks and you can immediately recrawl pages again whenever you want to confirm you've fixed issues. Many developers need to work on multiple sites as well.