Interestingly, in strict technical terms, : they are both forms of clipping. The difference in naming comes down to degree . Overdrive is typically the term used for lower-gain clipping that adds warmth and a slight "crunch," while distortion refers to a heavier, more aggressive and processed sound.
: In some versions, samples may play in a "round-robin" (randomized) fashion rather than responding to velocity, which can be fixed by adjusting the value in DirectWave. Corruption during Conversion Overdriven Guitar Dwp