I'd like the northwestern rail link simply because there would be a train station like 15 mins walk away and I wont have to drive or catch a bus to blacktown to get on a train
I admit that the Carlingford Line is completely isolated, but they don't have an awful space to expand out there (notably Carlingford) and also demand may not be be as high in proportion to the amount paid for the potential project.
I think North western as sydney is expanding in these areas and the western suburbs need a better way to get to the CBD with cheaper more fuel efficient transport and no traffic jams, it would also raise the value of my house substantially . But knowing sydney, if it does happen its not going to be efficient or planned correctly.