I enjoy sharpening knives with an Arkansas stone. I use DMT diamond sharpeners too with good satisfaction. I only use a carborundum stone for every dull knives, or between filing and an Arkansas stone. I like sharpening this way, the old way. I do most things the old way.

I've not used onion sharpener. But I've used a 1x30 belt sander. I can re-tip and re-grind the edge evenly on both sides.