To me anyway, the only advantages of the Ableton instruments are the integration into Live. They cut back the features of the AAS version to, you guessed it, fit into 128 parameters, and unlike a regular VST/AU instrument they beta tested the hell out of them for stability.
Re/preset changes: Urs heckman among others mentioned that the one reason he decided to make changing presets in Zebra, Filterscape etc. a mouse click instead of MIDI controllable via preset change commands was that with bigger soft synths with hundreds of parameters that would be morphed instantly by this, it was entirely possible to crash the plug in too many ways. I remember reading that about five years ago, and seeing it in action with reactor. Nowadays NI instruments in general haven't had any issues with preset changes crashing the host, probably as much to do with the CPU of my laptop now as their stability fixes over the years. I would be willing to bet money that at least half the reason for the way Live does program changes is to slow down the process, preset changes can happen at the speed of MIDI which is faster than you can mouse.
All this comes back to the same things over and over again. Live was audio only at first, and when VSTi's were added in v4, nothing changed with the MIDI on a core level. 128 parameters are the limit, and in many ways it remind me of Unix people who talk about the core of Windows being built up from some bad ideas to begin with. In many ways I feel they rushed into integrating VSTi, and now are stuck with this.
In that respect, it's another argument against the internal instruments, they bulit them to work with their own limits, so it's something that they can sell you that fully integrates with Live, unlike say my copy of Symptohm, which has at least double 128 parameters, and is crippled by Live to a degree because of that.
My reason for buying Kore, and pretty much never using Live's racks etc. was this. Kore hosts VST and VSTi's, and can address all the parameters of a plug in, plus you can map those parameters to the controller permanently for that preset or plug in. Sure, racks are more stable, but access to the parameters is as important to me.
I'll add in that despite all that, Live is still my favorite DAW, and I'm a DAWslut at this point, Logic, Reason, ReNoise, Digital Performer, and Live. At some point I'm going to par down here, to three.