Just to party poop a little, though I don't need it, the big X looks like the more interesting product. A real industrial production centrepiece with lots of touchable control and solidity. It has a clear purpose.
The smaller Live on the other hand has sort of missed the boat for me.
In trying to identify its key selling point/role: if I needed to decide on minimal on-the-road kit that fits in a laptop bag for a long time away between (a) the MPC Live or (b) ipad/laptop+irigHDpro+small controller, I'd go for (b) because I'm going to be bringing my ipad/laptop anyway for all that extra versatility and I'm not going to leave my ipad/laptop behind anyway. So it is really a decision between a small controller or the MPC Live in addition to the laptop/ipad I'm bringing anyway.
If I want to sit on the couch with something, I'd prefer it was moreso a focused instrument (like OT, RYTM, A4, MNM) to noodle on a few riffs & tracks, than a portable DAW with drum pads.
The MPC Live does look very nicely executed, but it isn't really bringing any new functionality to the table.
Funny thing is, I always wanted a near full DAW with good IO and a battery in an elektron sized box. Now that it's actually available, I'm not so sure!