Kensington Expert Mouse Trackball all the way. no Handedness limitation since it’s symmetrical, very fine tracking control, and chording, which adds two extra controls to the four buttons and scroll ring.
Only downside is it doesn’t have app specific profiles. (earlier versions did, like in 2005)
http://www.kensington.com/kensington/us/us/p/1444/K64325/expert-mouse®.aspx