I use a wide array of iThings... iPad Pro for FOH mix, iPad Air 2 on my mic stand to control my in ears and when I do run sound from the stage sometimes. iPad 2 for my keyboard player, iPad 3 as a backup. Guitarists use iPhone 5 and 6 for their monitor mixes.
There is no comparison between the pro and any other device. Never a glitch, never lag... very large control surface for finite adjustments - turn it to portrait mode and the sliders are bigger than my old consoles!
The iPad Air 2 is second best. Performance is awesome.
Great battery life on both of those even in full brightness on a sunlit day.
The iPad 2 is "okay". It works. It just lags a bit. I could not use it for FOH regularly for fear of it not responding instantly. It runs the latest iOS that can be loaded on it, and NOTHING else. It has been setup for maximum performance. It runs better on my dl1608 than my dl32r.
Ipad3 - meh. This thing has been disappointing. Running brightness up on it severely impacts the battery life. I can barely get a full show if in daylight (I usually run them unlocked and display on for 30 mins before a show, and then we might play two hours, or they might be on upwards of 4 hours.
The 3 also has really sketchy wifi, it will disconnect and have to re sync, sometimes within 30ft line of sight of the AP, the others have zero problems in the same environment.
If you can swing it financially, and want the best experience, get the pro. If not, or if you don't want something so huge, get the iPad Air 2....
