If you manage your sites with seo paid tools you will get higher ranks on search engines, a lot of traffic, many visitors. The paid tools have the big advantage that have a 24h support team ready to fix your coming up issues. Free tools doesn't have this, you hardly find someone to help you.
Another reason i recommend paid tools is the interface: very easy to use and integrate on your system, with an attractive design and very functional. Also they have up-dated algorithms all time maintenance to make sure that tool will give best results; if SE's introduce a new feature to classify the top sites, this will paid tools will take prompt action and introduce this too in their systems.