^ It's not necessarily their accent, but it's a combination of their deep voices (yes, they do have deep voices compared to other girls!) with that Brazilian accent which I don't like. Gisele is one Brazilian who I don't think sounds annoying when she speaks, however, her accent isn't as thick. And I've never heard Izabel Goulart speak, so I don't know how her Brazilian accent sounds. But I have a somewhat difficult time understanding Adriana and Alessandra because of their voice/super-thick accent.
By the way, I don't necessarily find Adriana and Alessandra annoying as a whole, I do like them. They should just keep their mouths closed.