Your first choice should always be your own server log files. These files – if collected properly – provide you with all the data you need to understand who is visiting your site, how often, and why.
There is a downside to using server log files for traffic analysis. You must know how to interpret the data. Even if you use a free reporting system like AWStats, you need to understand what the data is showing you. It also helps to be able to block rogue traffic.
If you compare an AWStats report to, say, a Google Analytics report, you’ll see a very different world from what Google Analytics shows you. Neither tool is perfect but whereas many people prefer the configuration of Google Analytics reports, AWStats has better data.
WordPress users should consider using Jetpack analytics. It’s more accurate for overall traffic than Google Analytics. Jetpack is a robust SEO and marketing plugin that does a lot of things for you, including generating XML sitemap files, social media sharing buttons, related posts widgets, and much more. You can also use Jetpack to verify your WordPress sites with Bing Toolbox, Google Search Console, and a few other services.
So, as you can see despite the fact that Google Analytics is so popular with web marketers, it’s not the only popular 3rd-party tool out there. They all have strengths and weaknesses, pros and cons. There is no 3rd-party analytics tool that is “best for SEO” – but there are some, that I mentioned you can use better than others.