For me it's the mini-4 (64Gb). I got the version with cellular but did not install a sim card. This gives me GPS so it shows up on the GO4 app. This becomes handy if I ever need to use "Find My Drone". I got it off EBay for 300 USD. It costs more than the mini-2 (which also is reported to work well) but I use it for more than a dedicated FPV for flying. I tried an IPad 9.7 but thought it was too heavy and really just too big. There have been rumors of a mini-5 coming out in March.