I have an iPad2 and an iPhone 4s. In the past I've played the game on a Nexus 7 as well.
My iPhone 4s plays the game very smoothly and I can burn through 50 stamina in under 2 minutes.
My iPad2 is a different story. The animations bog down performance and it takes forever to burn through 40 stamina. Maybe up to 4-5 minutes. Gross.
The Nexus 7 was okay, somewhere between the iPad 2 and iPhone 4s.
I would like to start another account and want to pick up a used iPod but I dont want to overspend as I will only use it for MW. Who plays on iPods? How would you rate it's performance? And what generation iPod do you use?? Thanks in advance! This question is probably best answered by those who play on multiple devices.