For those who have the freedom to decide what to use, I recommend looking into rolling your own. Especially if you're writing back-end services for your app anyway. After Google shutdown Fabric.io, we asked ourselves why even rely on 3rd parties for analytics. All we really wanted to know is basic usage statistics, like uniques, sessions, events. Turns out to be just a few days of work for what amounts to a CRUD serv…
There's a reason that there are profitable companies dedicated to building stuff like this. It's really hard to get right in a scalable way.
Unless you're already a multi-billion dollar corp (and how did you get that big without analytics), it's a no-brainer - this is something to buy, not to build.