I am still getting the last bit of mileage out of my surviving Bachmann models, and currently have 2 replacements from Hornby, for those that have already 'died'. (The split chassis of the Bachmann wear out rather faster than a conventional steel axle chassis.) No doubt about it, the Hornby is a much superior model; but it is far from perfect, and I am now going to wait to see if Bachmann bring out a yet better model, because the Hornby leaves plenty of opportunity for improvement.
The Hornby chassis has a mechanically inept motor mount, live chassis block instead of a properly soldered connection to the pick up one side, inaccurate wheels (the exterior form of the Bachmann A4 wheels are a much better representation of the prototype) not the most convincing valve gear, the poor compromise of a flangeless fixed truck (Bachmann on their A1 have a better solution) and a very dated loco to tender coupling. The body forms of loco and tender are overall very good on the Hornby, except for the different sized exhaust apertures for the Kylchap ejectors, a very strange mistake, but at least easy to correct. So it is currently the best available, but as Bach have announced their intent to replace their split chassis models with all new current standard models, it won't be top of the heap indefinitely.