What ASO Tool should I use?

This is a tricky question and depends on what KPI’s and metrics you want to track. It also depends on the size of your operation, and ultimately your budget. I personally prefer: Mobile Action and Sensor Tower. Both of them are great tools and both have a “free-mium” model where you can start with a trial and upgrade when the trial is up. App Annie is prohibitively expensive and your budget would best be spent on an ASO expert. Speaking of which….