They arguably sound "better" because of reduced microphonics.
But musically I did not hear any difference between my white 9963 IEMs with a rubber cord and my black 9927 IEMs with a fabric cord (both IEMs have about 2 months of use).
EDIT: Doing a comparison right now I think my black 9927 IEMs are a bit more "v-shaped" than my white 9963 IEMs - the bass seems a bit stronger and the highs seem to have a bit more sparkle. However, considering how inexpensive these IEMs are I wouldn't be surprised if this little difference is just a case of variations within the manufacturing.
EDIT 2: Yeah, my white 9963 IEMs actually seem to be more neutral-sounding, the midrange in particular seems to come through more clearly. Perhaps I've used my white 9963 IEMs more frequently and therefore they have been "burned in" more due to said more frequent use? I say this because, in an un-burned-in state, the bass and treble on the Monoprice IEMs are known to be a bit too much, and will settle down after being burned in.