I think ISO owns Bin/Cue. Here's why.
1) ISO's are smaller. A full CD is a 700MB ISO or an 800MB BIN.
2) Nobody shares CUE's. For some reason unknown.
3) Very few people have realized that a CUE is merely a text file and they could just post its contents and the filename.
4) They're trickier to burn. ISO's require one less step.
So... why is BIN/CUE the format of choice? If I get a BIN/CUE I convert to ISO because I value my space; no sense wasting it for nothing.