I think there's a disconnect between what you're reporting, and what I'm asking. But your comparative observations are appreciated.

You're reporting the accuracy of what you hear when listening to radio station WTOP or XM radio, yes? I'm asking for comparisons of 'traffic feed' data transmitted and picked up by GPS units via the three means, FM TMC (Traffic Message Channel), Satellite Radio, or MSN Direct. For what I'm asking about you'll never hear an audible signal in the RF bands, it will be all data.