yeah i think the general consensus on modular helmets is that they are quite a bit noisier.
there may be exceptions though. schuberth make a really quiet one (but it's expensive).
with regards to safety, i don't think they can ever truly be as wholly-rigid as a proper full-face helmet, but they ALL have to pass the safety standards before being put on sale and there are plenty of people willing to give their stories of a modular helmet doing it's job admirably (a few from this site, i might add).
so it probably comes down to a comfort choice. can you deal with the noise? does the helmet fit your head-shape?
it's unwise to decide on a helmet before you've tried it on. different brands make different shaped helmets and you might never be comfortable in certain brands, no matter how plush or expensive they are. that's just the way it is.
as the other guys round here have said, go try some on. it's fun! run around the shop making vroom vroom noises =D