I already own an Ipad, so then it's the price of a soundcard
including enough ins/outs + midi capabilities + portability + midi (pad) controller.
I know the MPC live has really a lot to offer, but it's all about what are your needs, how do you like to use it.
If I recorded some loops, sounds etc. and I just want to edit these, I just can take the Ipad with me, no hassle with a bulky box, that's what I am after, a more flexible system.
As an instrument, for making beats, playing live etc I have my OT + AR, these are the base of my rig.