When I chose mixpanel, it was over flurry - Google still hadn't launched their mobile analytics offering yet.
At the core, mixpanel uses events vs. pageviews to understand the data you're getting. So for funnel conversion, this is slightly better since you are counting the click/tap events that take you to the next step, vs. looking at page A and page B and then deducing the conversion %. But not earth-shattering different.
But what mixpanel does that I haven't seen anyone else do is have a "People" tab where I can see the data history of each registered user. Since we were dealing with real-money transactions, this was incredibly important.
Hope that helps