one "big" advantage with T29 is its smaller size and the weight.
T29: 44gram
m6: 56 gram
I own both players and tend to pick up the T29 when its time to leave because of the size and weight factor.
but, m6 is a damn niiiiice player too ...
Id say: if you have the money go for m6, if you want a cheaper, stylish and smaller player get a T29.