It's mostly that hardware makers invested more time and money into the algorithms to make them more pleasantly sounding. Many software synths are one-man projec

It's mostly that hardware makers invested more time and money into the algorithms to make them more pleasantly sounding. Many software synths are one-man projects which has to do it all (DSP, UI, ...) Hardware makers also have proprietary institutional knowledge, since you can have a couple persons who researched synthesis methods for 10 years. They also work with users to tweak the sound and interface to perfection.