There is no dispute about the convenience of modular helmets. You can take photos, get plenty of air while riding in city traffic, talk to mates and even fill your fuel tank without having to take off your helmet. (Note that there are few helmets where the chin bar locks in the up position and legally permits the rider to ride with the helmet in this position.)
However, modular helmets have inherent design issues that reduce their safety levels.
Instead of the crash-resistant integrity of a full shell, they have two parts held together by a hinge and clasp mechanism that uses a combination of plastic, fibreglass and flimsy metal.