I was surprised to note the omission of First Greater Manchester's 350 service from Oldham to Ashton-under-Lyne. It offers a longer - though considerably more scenic - alternative to the 409 service between the two towns.
The full route takes in breathtaking views from Scouthead towards Oldham, Manchester city centre, and further afield. Between Greenfield and Micklehurst, glorious views of Roughtown and Lydgate in the distance. If you catch any of the part route journeys from Micklehurst you miss the stunning views from Saddleworth. Instead you also get superb views of Manchester city centre and the Winter Hill transmitter as well as Hartshead Pike (a short walk from one of the stops on Mossley Road).
The 343 (or the 340 on Sundays, early evenings, and Bank Holidays) offer wonderful views of Mossley which can be seen from Huddersfield Road. One stop, on Brushes Estate, is handy for walks around the Walkerwood and Swineshaw reservoirs.
With the 350 there's a greater chance of finding double decker buses along the full route. On the 343, usually Optare Solos or Enviro200s (operated by Stott's Tours). On the 340 (First Greater Manchester by evening, Stagecoach Manchester on Sunday and Bank Holiday daytimes), single decker buses are commonplace.