Google Analytics is Google's service for tracking who visits your Web site. reinvigorate is another service for tracking who visits your Web site. reinvigorate is currently in beta, but I am assuming that it remains free like it was before it went under re-construction. reinvigorate is currently invite only, but you can give them your e-mail address to be put on the invite list.
Google Analytics has three different "views": Webmaster, Marketer, and Executive. For my usage, I stick with Webmaster and Content Optimization sections. reinvigorate contains the same information from those two sections and more, which I will go into later.
It has been a long time since I setup Google Analytics. I remember it took a while before it finally picked up traffic. Maybe this has improved since then. reinvigorate started working right away.
reinvigorate has a nice, attractive design, reminding me a little bit of Apple's Aqua. Google Analytics looks plain in comparison.
Both Google Analytics and reinvigorate allow you to look at traffic stats in an hourly, daily, and monthly fashion, with reinvigorate also including a yearly look. The time range in Google Analytics carries over to other statistics, while reinvigorate appears to look at everything else since you start their service. For reinvigorate, this can be great if you want to look at where all your visitors are coming from, but not as great if you are trying to compare browser usage between two different time periods.
When it comes to looking at browser usage, I prefer reinvigorate's method of showing everything, including version breakdown, on one screen instead of Google Analytics' tree level method to get that version information. When it comes to operating systems, reinvigorate gives a bit more information, showing that a visitor had the x64 edition of Windows Server.
Both services will give you screen resolution information. Google Analytics gives a bit more useful information here with screen color information while reinvigorate gives screen aspect ratio information.
I like reinvigorate's reports of where visitors are coming from, even though it is split amongst a few screens. Ironically, reinvigorate uses Google Maps to show where users are coming from, while Google Analytics doesn't use it at all.
Google Analytics tells you who has Java enabled; this information isn't available in reinvigorate. reinvigorate will tell you what version of .NET visitors are running. I question how useful this is, especially since it is limited to visitors using Windows and IE. Substituting Flash version information like Google Analytics would be much more useful here. Also strangely missing from reinvigorate, but found in Google Analytics, is connection speed.
While Google Analytics will tell you what site someone came to yours from, it only gives a domain name. reinvigorate goes much farther, showing the exact URL they came from to get to your site.
Another plus for reinvigorate is showing live activity on your site. But what really sticks out at me is reinvigorate's report that shows you which search terms from various search engines brought people to your site. This can be great information to find ways to drive more visitors to your site.
Right now I would recommend using both services for gathering traffic information for a Web site. Both have features the other service doesn't that are important for running a Web site.