I am trying to decide on a solution to better track our user data. We need to track which google ads are leading to signups, and which signups are performing various actions on the site. We then need to visualize this data in various ways. We also need to run A/B tests on features and content, to track which ones lead to the most paid conversions.
Functionally, Amplitude and Mixpanel are incredibly similar. They both offer almost all the same functionality around tracking and visualizing user actions for analytics. You can track A/B test results in both. We ended up going with Amplitude at BaseDash because it has a more generous free tier for our uses (10 million actions per month, versus Mixpanel's 1000 monthly tracked users).
Segment isn't meant to compete with these tools, but instead acts as an API to send actions to them, and other analytics tools. If you're just sending event data to one of these tools, you probably don't need Segment. If you're using other analytics tools like Google Analytics and FullStory, Segment makes it easy to send events to all your tools at once.
Another option you might consider is Google Analytics App+Web.
It is a new type of Google Analytics property which is event-based (like Amplitude and Mixpanel). In App+Web you can collect exactly the same data and in the same format as the other 2 tools mentioned.
The great things about it are: - it is free - there is a free integration with BigQuery (though you'll need to pay for BigQuery, but for most SmB's it is peanuts - $5-30 a month)
Not so great: - reporting side is pretty buggy (App+Web is very new).
So if you are ok building your reporting in something like Google Data Studio, App+Web will be a great option. Your data analyst will especially be happy to have all the data in SQL format (BigQuery).
If you choose App+Web, then you can use Google Optimize (also free) as an A/B testing solution.