Buy a modular if you talk to people at stops, wear glasses, tour, commute in traffic, or want one helmet that is both a full-face and - with the right mark - an approved open-face. The pick is the HJC RPHA 91: ECE 22.06 with P/J homologation and an independent SHARP 4/5 score. Buy a full-face if you want the lightest, quietest, structurally simplest helmet for the money - the AGV K6 S is about 1,255 g with DOT + ECE 22.06 and a perfect SHARP 5/5. Both of those are good answers. What follows is how to tell which one is yours.
We have not crash-tested any of these helmets. The certifications come from the standards bodies and each maker's published homologation and describe the US-market build; the SHARP scores and latch percentages are SHARP's published results, all cited at the foot of the page.
The format difference in one paragraph
A full-face is one continuous shell. A modular (flip-up) splits the chin bar onto a hinge so you can raise it at a stop. Everything else follows from that: the modular has more parts, a seam through the shell, a latch, and usually 100-300 g more weight - and in exchange it gives you a face you can uncover without taking the helmet off. Our helmet types explainer places both against open-face and adventure formats.
The safety question, answered with the two numbers that matter
One: the P/J mark. Under the ECE standard a flip-up can be homologated as P (approved only as a full-face, bar down while moving), J (approved only as an open-face), or P/J (passed both, so it is simultaneously an approved full-face and an approved jet). A modular carrying P/J was impact-tested with the chin bar in both positions. That is the mark that makes a flip-up a genuine full-face rather than a compromise, and it is printed on the label most buyers never read.
Two: SHARP's latch percentage. SHARP publishes, for flip-ups only, the percentage of its impact tests in which the chin bar stayed fully locked - and deliberately does not fold that figure into the star rating. It is the single most useful number in this category and almost no review quotes it. The RPHA 91 holds 4/5 stars with the face guard fully locked in 80% of impacts; the European Shoei Neotec 3 holds 5/5 with 93%. Our are modular helmets safe? page works through what those numbers do and do not mean.
Put together: a P/J-homologated flip-up with a published latch percentage is a well-evidenced helmet, and the honest summary is that the structural simplicity of a one-piece is a real advantage that a good modular narrows rather than erases. If you want the strongest available evidence in a one-piece, that is the K6 S at 5/5; if you want it in a flip-up, the RPHA 91.
Weight, noise and the things you feel every ride
Weight is the clearest practical gap. The full-faces here are about 1,255 g (K6 S) and 1,385 g (RF-1400); the modulars are about 1,740 g (RPHA 91) and 1,880 g (Neotec 3). Four to six hundred grams is a real difference by hour six, and it is why lightweight full-face buyers rarely end up in a flip-up.
Noise is less one-sided than the format suggests. A modular has a chin-bar seam that can whistle, but the quietest helmets we cover include premium touring modulars built around sealing - the Neotec 3 is the benchmark. Meanwhile the dominant noise source above about 40 mph is aerodynamic and heavily influenced by your windscreen, not just the helmet, as our quietest-helmets guide explains. Earplugs beat format either way.
Glasses, drinks, conversations and gas stations are where the modular wins outright. Putting glasses on with the chin bar raised is simply easier - which is why our helmets-for-glasses guide leans modular - and so is talking to someone without a muffled shout. If you ride with a pillion, in city traffic, or in a group, these small things are the ones you notice daily.
The four helmets, and who each is for
HJC RPHA 91 (modular) - ECE 22.06 P/J, SHARP 4/5, 80% latch, sun visor, about 1,740 g. Who it is for: the rider who wants flip-up convenience with the best documented safety story in the format. See the RPHA 91 review.
AGV K6 S (full-face) - DOT + ECE 22.06, SHARP 5/5, carbon-aramid, about 1,255 g. Who it is for: the rider who wants the lightest, best-evidenced helmet here and does not need to open it. No sun visor, sporty fit - the K6 S review has the detail.
Shoei RF-1400 (full-face) - DOT + Snell M2025, about 1,385 g, and its European twin the NXR2 scored 5/5 with SHARP. Who it is for: the sport-touring rider who wants a refined one-piece and values Snell. See the RF-1400 review.
Shoei Neotec 3 (modular) - the quiet-touring benchmark, about 1,880 g, and in the US a DOT build (the European unit is ECE 22.06 P/J, 5/5 SHARP, 93% latch). Who it is for: the long-distance tourer buying silence and comms integration with eyes open about the US homologation - the Neotec 3 review spells it out.
So, modular or full-face?
Commuting, touring, glasses, group riding, or you want the option of riding with your face open? Modular, and make sure it says P/J. Fast road riding, track days, hot weather, or you simply want the least helmet on your neck? Full-face. Still torn? Weigh how often you actually stop: the flip-up's whole value is in what happens when the bike is not moving. For the full field in each format, start at the modular hub or the full-face hub.
If you buy modular, check these three things
Is it P/J? If you intend to ever ride with the bar up, this is not optional - a modular without the P/J mark is approved only as a full-face, whatever the marketing photograph shows. The label on the chin strap tells you.
Does the bar latch positively? You want an unambiguous click, one-handed, in gloves. A mechanism you have to fiddle with is a mechanism you will leave half-closed.
Is there a SHARP latch percentage? Not every model has been tested, but where it exists it is free evidence about the one component that is unique to this format.
If you buy full-face, check these two
Can you get it on and off over glasses? A one-piece makes you thread eyewear through a closed aperture every ride. If that annoys you in the shop, it will annoy you for years.
Is there provision for the shield you will want? A Pinlock-prepared shield and a sun solution (an internal visor, or a photochromic shield) are what make a one-piece liveable year-round - see the Pinlock guide and our sun-visor picks.
And in both cases, fit decides more than format. A correctly-shaped helmet is what makes any certification real - our head-shape guide and measuring guide are the two pages to read before you spend.
