Cantabile Pro is great for playing virtual-instruments live.
Virtual-instruments are organized like a virtual Rack of Hardware Synths.
You can create whatever advanced splits/layers necessary.
CPU use is very efficient; only the virtual-instruments used in each patch ("Scene" IIRC) are actually running.
Another application to check out for playing live is Ableton Live.
Don't dismiss it thinking it's only for triggering loops. It's *FAR* more advanced than that.
Watch a few YouTube videos of what keyboard players are doing with Live.
It's pretty amazing. Seamless patch-switching (between advanced splits/layers), advanced click-tracks, etc.
We use Ableton Live for triggering keyboard parts and samples at gigs (using two small MIDI controllers).
Amazing flexibility, quick/easy to rearrange set-list, and rock-solid...