For me the four main advantages for hardware over software are;
1. Transportability - I know the above poster is right in saying that you can take a small keyboard and laptop to the park, but when I go to a gig, I prefer just bringing something like the Kronos, where all I have to do is switch it on. Not hook up the audio and midi interfaces, boot up mainstage/whatever, load up all those patches etc. I've done that and it does have its uses, but it's just ten times simpler using a hardware synth or workstation.
2. Coherence of sound - mr. Rudess also mentioned this briefly in the long launch video and I thought it was a very astute point. With an instrument like Kronos, all the sounds are somehow in balance much more than with a random collection of VSTis. I don't mean that they all sound the same or have a particular Korg sheen - even when I load samples in my TrEX it is somehow still "part of the instrument". It's hard to explain I suppose. I did quite a few gigs where I was required to play Mainstage with a lot of different VSTis and I had a constant struggle trying to get them to "play nice" in the mix and respond somewhat uniformly to my PC-600 controller.
So while it is true that softsynths tend to offer a wider scope of sounds and better sounds in most categories, that does not always help the live user.
3. Reliability - although I have to admit that Mainstage nor Ableton have never catastrophically failed me, something in me is still nervous when I use them over a piece of dedicated hardware. Both Mainstage and Ableton HAVE crashed while I was preparing stuff at home, for instance. The worst that has happened to my TrEX was that the sustain pedal hung. Switching sounds back and forth fixed it. I used Brainspawn Forte a year or two ago and got a blue screen of death during a gig. Not fun.
4. Control and programmability - the larger screens on computers are nice, it's true. But I HATE fiddling with the mouse to change some filter cut off or LFO rate. I need knobs and sliders and preferably a touch screen. I know a dedicated controller would largely fix this (I didn't do much with Ableton till I got my APC40) but at what point does software then become hardware again? Think of the MS20 controller for instance.
Universal controllers don't cut it for me personally, simply because the random assignment of faders and knobs doesn't correspond visually (and thus intuitively) with what's on the screen.
Well, this turned out longer than I thought it would. I guess my mind is made up even more that I already knew about wanting a Kronos!
