Yes, they have somehow the same style (clothing and music) , but Waits isn't a one-man-band, and also he acts in movies, because I remeber now that I saw him on the book of eli. But his voice is loooowww, while SOD's voice is higher than his.
SOD even uses an octave pedal sometimes, for his harp and his voice.
On this video he sings really high
[video]http://www.youtube.com/watch?v=QrkdNPf3BVc[/video]