I don't even think that the Bachmann model has an advantage in the wheels/valve gear area. Far from it. The valve gear has that silly screw in the middle of the crank, plus usually a screw on the crosshead. Regarding the wheels, the tyres are too shallow, which makes them look totally unconvincing, and the tyres have a weird curved profile on their surface, as if they've been flooded with too much paint. This means that while with a Hornby model only the bogie wheels need changing and the driving wheels painting, with a Bachmann model by contrast (LNER at least) the driving wheels have to be changed too - thus negating the price advantage. Not that there is much of a price advantage anyway - there's no need to pay more than £92 for a Hornby B1.
To plagiarise a rather witty post from the Bachmann camp above, the Bachmann model looks like a Hornby one ... but with rubbish everything.