This is the lightweight sport-touring decision at the top of the class. The AGV K6 S and the Shoei RF-1400 are two of the lightest, best-certified full-face helmets money can buy, and both are genuinely excellent. The difference is a certification philosophy and a fit shape — and once you see it, the choice usually makes itself.
Certification: the K6 S has the on-paper edge
The K6 S carries genuine US DOT + ECE 22.06 and a perfect 5/5 SHARP score — the current rotational standard and top independent data, on the US helmet. The RF-1400 is a DOT + Snell M2025 build; its European twin, the NXR2, is also a 5/5 SHARP helmet, but the US RF-1400 itself is a Snell build, not 22.06. Both are superbly protective; if you want genuine 22.06 with independent SHARP data on the exact helmet you buy, the K6 S has it outright.
Weight: the K6 S wins, barely
Both are exceptionally light. The K6 S is around 1,255 g in carbon-aramid, one of the lightest full-face helmets on the market; the RF-1400 is around 1,385 g, also very light for a fiberglass-composite lid. The K6 S is the lighter of the two, but you're splitting hairs — both feel featherweight next to a touring helmet.
Quiet, fit and character
The RF-1400 is the more overtly touring-refined of the two: wind-tunnel-developed for lower drag and lift than the RF-1200, with an airtight window-beading system aimed at wind noise, and a fit Shoei pitches at intermediate-oval heads. The K6 S is sportier, with a racing-derived huge field of view and a snugger fit that suits sport riders and can feel tight for round heads. Neither has a sun visor. Which you prefer is really about whether you lean sport (K6 S) or sport-touring (RF-1400), and which brand's shape fits your head.
Everyday use and the shield systems
Neither of these is a touring helmet, so neither has a sun visor, and both ask you to run a tinted shield or sunglasses in bright light. Both shields are Pinlock-ready and swap easily, and both interiors are removable and washable. The real everyday difference is character: the RF-1400 feels like a helmet engineered to be quiet and composed for hour after hour, with that airtight window beading doing real work; the K6 S feels sharper and more alert, with its huge eyeport giving an almost helmetless field of view that sport riders love. On a fast road you notice the K6 S's view; on a long slog you notice the RF-1400's calm.
Price tends to track this too — the carbon-aramid K6 S usually sits a little above the composite RF-1400 — but they're close enough that cost rarely decides it. That's the healthy way to approach two helmets this good: buy on fit and on which certification story you value (genuine US 22.06 with a 5/5 SHARP on the K6 S, or the RF-1400's Snell build with a 5/5 SHARP twin), rather than trying to save a few dollars. Both will be with you for years.
The verdict
Want the lightest helmet, genuine ECE 22.06, a 5/5 SHARP score and a sporty wide-view fit? The AGV K6 S— it's the safety-data leader of the class. Want the more touring-refined, wind-tunnel-quiet helmet, and a Snell build with a 5/5 SHARP twin satisfies you? The Shoei RF-1400. Both are outstanding; let fit shape and certification philosophy decide. Read the K6 S review and RF-1400 review for the detail.
