There are two main differences between google analytics and mixpanel tracking.
- Service Charges
- User Tracking
Google analytics is a free tool and anyone can use with a little knowledge and the internet is full of google analytics trainings. On the other hand Mixpanel is a paid tool and is used by very low number of people and anyone with knowledge about google analytics can easily learn mixpanel.
Google Analytics relies exclusively on keeping track of users via a cookie (the average time of a cookie expires in 30 days).
With Mixpanel, you can utilize a user_id or any other id that makes sense for your business which will always last longer than a cookie.
Read more about difference between Mixpanel and google analytics.