Has anyone else noticed that G Analytics does not really capture every visitor to a site? Couldn't that be an issue if doing SEO for a client when you use GA as a starting reference point?

What other tool do you use to determinate G Analytics isn't tracking all visitors?

All I know G is very accurate in tracking all real unique users, maybe a lot of bots aren't counted for the stats that's where difference came from.

Google Analytics doesn't count visitors who have JavaScript disabled...There is a script you can install to beat that problem BUT then your visitors are redirected and shown the "install Java" prompt, and who wants that?!

Maybe try an additional stats counter like Awstats or Webalizer, or do some research on paid providers. Google Analytics is a great FREE tool...Keyword, FREE lol.

One of my clients contacted them and apparently they are 99.6% accurate at counting visitors

LOL! 99% accurate. (Im not laughing at you but at G)
you should read all of the threads on google about this topic. That theory about Java script is true.
that is a pain in the ass! Godaddy analytics is quite expensive and they charge per website. Ill look around.