I prefer natural materials, my favorite is stag, followed by horn, bone, and wood. They have a much warmer feel to them. Although in some uses a synthetic handle may be more sensible, e.g., a knife that will be in the bottom of a tool box, pack, etc, where it may get dinged around or left wet.
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Die Entropie der Welt strebt einem Maximum zu - R.J.E. Clausius