For me, Zo, it's very easy to set up Ableton for live performance, uing VST
and HARDWARE instruments, using VST and EXTERNAL EFX units with totally werd combinations - and to still have full control over whole project.
Ableton has INPUT GAIN (in opposite to pour SONAR), has better "matrix", has good as hell MIDI mapping abilities.
TRY IT BY YouRSELF.
If you'll go thru different DNA (just to underline: Ableton is generally for LIVEACTS purposes, and then for production purposes), the rest is pure fun and creativity.
And you'll maybe start to wondering, why "so simple" software has these all goods and "very sophisticated and pro" Sonar - hasn't.
For better examples what you can do with Ableton - go to Ableton's homepage. Look at MIDI mapping, warping (no issues with disappearing knots), efx combinations, drumsets and instruemnts.