W1 vs W2
The water-hardening brothers, separated by a fraction of vanadium. W1 is the plain original — pure simple carbon, sold everywhere as drill rod; W2 adds ~0.2% vanadium that pins grain growth and sharpens hamon activity, which made it the modern clay-quench darling. Everything else — the fast quench, the keen fragile edges, the enthusiastic rust — they share like the siblings they are.
Quick Verdict
Building a hamon showpiece: W2 - the vanadium grain refinement draws the most vivid activity in the business and forgives an overheated forge cycle. Everything else water-steel: W1 does the same jobs for less money with better availability, especially in drill-rod rounds. Many shops stock both and let the project choose.
Toughness
Effectively even at equal hardness and grain size - the practical difference is that W2's vanadium HOLDS grain fine through sloppier thermal cycles, so real-world W2 blades are often tougher than real-world W1 blades made by the same hands. Discipline erases the gap; neither is a chopping steel through-hardened.
Edge Retention
A near tie with the same character: keen fast edges, quick to dull in abrasive media, instant to strop back. W2's finer grain gives a marginally more stable apex at razor hardness. Nobody chooses between them on this column.
Corrosion Resistance
Identical enthusiasm for rust - zero protection, patina-or-oil ownership, no difference worth a sentence.
Heat Treat
Same protocol: ~1450-1475°F, short soak, fast oil for blades (water/brine for thick sections with crack risk accepted), immediate double temper, 60-64 working range. Both are premier shallow-hardening hamon steels; W2's vanadium draws crisper, busier lines and tolerates forge-heat wobble better. W1 rewards tighter cycling with results close behind.
Grinding
Both machine and grind like the simple steels they are - dead-soft anneals, friendly belts, easy finishing. W1's drill-rod availability is the practical win: rounds for integrals and tools off any industrial shelf, in diameters W2 rarely ships.
Best-Use Scenarios
W2: hamon showpieces, bowies and camp knives with soft spines, anything where the quench line IS the product. W1: budget hamon work, razors, kitchen slicers, drill-rod integrals and tooling, known-steel first knives. Both: keep them dry.