I only use the free version of ALL IN ONE SEO because I don’t have need of the paid version but I can say it’s the best and easiest to use of all the ones I have experimented with. And they even provided me with some free tech support when I was having issues. So I would recommend them above all the others and, if you have need of advanced statistical data for your site, I imagine the paid version is very much worth it if only for the quick and friendly tech support you will receive. Oh and I used it on multiple sites as well.