Btw, it sucks on both.

Today I used my K850i from SE as Radio (it also has RDS).
I had to place the N900 right on the headset cable (the 'antenna') to have clear audio in the 'radio' (the K850).

If I kept the N900 in my hands, sitting at the table, thus few cm away from the 'radio', the quality would drop a lot.
Rotating the N900 did affect the quality (from nothing to good quality) of the audio in the 'radio'.

And I was in my room... not in a shielded car.