One of the mistakes Mixpanel made was to position themselves as a “better” Google Analytics. That meant a generous free tier without the benefit to search that Google gets.
Amplitude, from the moment I was aware of it, was more about productizing the Facebook/Zynga style product analytics approach.
I left Zynga for an early startup in 2011. At that time, I tried to use Mixpanel for acquisition and retention analysis - it fell woefully short. I wasn’t able to use any of the built-in reporting.
Meanwhile, I have been a mega fan of Amplitude from the first time I ever used it. It was built for the “product data” use case first, not as a Google analytics replacement. That positioning made it easier for them to demand premium pricing.