It makes much more sense running East Hills Line services via Airport in the off-peak. The services in the proposed timetable that go Wolli Creek then Holsworthy already miss Riverwood - East Hills from the more common stopping pattern, so their loads shouldn't be high. By making additional stops via the Airport Line, those services can be much more useful for airport commuters. There's a few other reasons why it makes sense to travel via Airport rather than Sydenham.
- Makes interchanging much more simpler for people on the Illawarra Line, by interchanging at Wolli Creek. No need to figure out whether to go to Sydenham or Wolli Creek to interchange.
- Now that the Airport Line sees 8 trains per hour around the clock, this hopefully will encourage more people to catch a train to the airport with such regular services. Running the expresses via the Airport helps contribute to those services.
- Avoids conflict with the Bankstown Line at Sydenham, making it easier to schedule and reducing the impact of any delays on one part of the line.
As far as the Bankstown Line goes, I think there's been some hits and some misses. As lyyjjimmy says, the frequent hour has been extended and there are more services overall. I think a lot of commuters will also appreciate the "via Town Hall" destination of trains now as well.
But I think the revised limited stops services, which have become much more numerous, are a severe miss.
I don't see why Yagoona and Wiley Park should no longer have the limited stops services.
For one, the current limited stops services seem to get most of their customers in the Bankstown to Campsie segment. Hardly anyone actually uses the services to get to/from Liverpool as the South Line is still faster. Skipping Yagoona provides no time saving to those passengers boarding further towards the City and likewise to a lesser extent for Wiley Park. The people from those stations, even though they aren't as much in number as the other stations, will still have to face a 30 minute+ journey on the all stops services now.
Furthermore, considering that Yagoona and Wiley Park are much further from the City than say Marrickville or St Peters, I don't see why those two stations were substituted out for Marrickville and St Peters. Marrickville and St Peters already have it pretty good considering how close they live to the City, especially St Peters. Both stations are within 15 minutes of Central. Adding those stops so late in the journey also costs the already-full train of passengers additional journey time, which is something that would not have occurred as much with the additional stops at Yagoona and Wiley Park, since there would have been numerous passengers boarding after those stops at Bankstown, Punchbowl, Lakemba, Belmore and Campsie.
Furthermore, the people who board at Marrickville and St Peters get hardly any benefit from catching these limited stops services at all. The people at St Peters and Marrickville only have one station skipped (Erskineville) from the normal service, providing them with a 1 minute gain at best.
I think that the current limited stops services have a much better stopping pattern - all to Campsie, Sydenham, Redfern, City and back. It makes much more logical sense in that those who live further should get the faster service, not people at Marrickville or St Peters who not only have a much shorter journey to make, but also hardly get any benefit from the limited stops service, and also slow down the journey time for the commuters further away from the City.
As another note, it seems Warwick Farm has been re-added to the Bankstown Line for regular services. That was a very strange anomaly of the current timetable.