Well, playing and recording a live instrument is much more expressive for many reasons. But the biggest thing are these little random bits and noises that can b

Well, playing and recording a live instrument is much more expressive for many reasons. But the biggest thing are these little random bits and noises that can be present when recording with a microphone and inconsistencies such as pitch fluctuations. This can be emulated with soft synths and samplers but with many limitations. When I produce music digitally, I usually get the most interesting results by randomising devices. For example, in Ableton Live there is a device called "Device Randomiser" that can randomise other devices. A few of these in a chain can produce crazy sounds over time. Then these can be used together with more traditional soft synths, for example by using them as an external vocoder signal.