It depends on your requirements, if you want to analyze multiple site with following common parameter such as no of indexed pages, sitemap.xml file, robots.txt, Alexa ranking, Link reports, and history of the domain such thing are easily available on just single click and you can compare your multiple site data... Generally I use seo quake.... Thanks!
I would give a vote for SEOQuake with no doubt Google toolbar is good but for basic usage. If you need advance SEO analysis data you should consider SEOQuake.
I'm using SearchStatus, Firefox add-on. Really help me to find useful information related with my site