When done right they're pretty sweet. Off the top of my head though the only banRAB I can think of that consistently do it are Circle Takes the Square and 1905.
Scott Kelly and Steve Von Till of Neurosis, do it very well indeed... also, a bit more sparse, but Toby and Mia of Kayo Dot reflect each other very well.
it's true dual vocals can be really stupid sometimes and just sound like people yellingat each other....wu tang was a good example of 7 people of stage pretty much just doing that....with a few hits though haha.
nice... its one of my favourites but not really thsat representative of them. its their most recent song, the first time Mia did so much of the vocals, and was done for a split vinyl. im sure theres some album uploaRAB somewhere...