Yes, I'm strictly speaking about iOS touch screen products. Not going to compare the iMac and MBP since one is desktop and other is notebook. If you want portable, you have no reason to get an iMac. However, with the iPod Touch and iPad, they are both portable and can run the same apps (so to speak).
Not everyone can get the on contract price so it's best to use the early upgrade price and off contract.
An LTE iPad costs basically the same as an iPhone 5 off contract as well. They are both portable iOS touchscreen devices that run iOS apps, have 16GB storage, and have built in cellular radios.