The Official Ozzy Osbourne Site | The official Ozzy Osbourne site

the three main singers...

Ozzy - uniquness is kind of vague...he did have the ability to sing from soft to heavy (ie Solitude to Symptom of the Universe) and his voice tone is different on each album. which gives him more to offer than any other singer...that and his static stage performances. what always puts him on a higher level than the others is that he was the original singer and his ability to suite his voice towards the music

Dio - Dio was in Rainbow before he joined, so he was well known and most likely brought his fans with him. no other singer could have pulled off what he did when he joined Sabbath and it just goes to show with Heaven and Hells first track Neon Knights, which grabs your attention and holds you in place until the album is over. in my opinion, his voice was the best that Sabbath ever had, but that doesnt make him my favourite. maybe if Dio recorded more with Sabbath, he would have had more albums or songs to go wrong with like the Oz eras last two albums..or maybe not.

Tony Martin - underrated, no doubt....i think mainly because nobody knew who he was. technically, he may be a good singer, but i dont think he was right for Sabbath. you said he has versatility...to me, he sounds more like Dio if anything, and his performances of the Oz era material is just painful to listen to (same for Dio)