I have no idea how many organizations are including the latching mechanism in their testing of modular helmets now because I haven't shopped for a helmet for a while.
The UK, under their SHARP helmet testing program, was one of the first, if not the first, to test and rate the ability of the latch mechanism to remain latched under impact. They started doing this because all of the other testing agencies such as DOT and Snell tested modular helmets the same way that they tested full-face helmets, and did not test the integrity of the latch mechanism specifically.
Their website is below.
SHARP
I have a modular helmet. I find it very convenient at gas stops, stopping for a quick drink, or when trying to talk to other people, etc.. In any instance where you want to do something but do not want to remove your helmet, it is very convenient. I also find it easier to put on and remove than a properly fitting full-face. I also find it easier to put glasses on than when wearing a full-face.
I never ride with it flipped up, not even at very slow speeds. If during your normal riding you very rarely remove your helmet for any reason until when you normally would at a stop anyway, then the benefits will be less of a convenience to you.