Here are some picture of three different brands of 3-rail Birneys (left to right): Lionel 1990s, Corgi, and Bowser.
LIONEL
Pros: close to scale length, reversing bump action.
Cons: Too wide, rides high, lacking detail (more recent ones have better poles and window grills). Ironically, earlier Lionels have the right steps.
CORGI
Pros: close to scale length AND width, great detail, complete interior.
Cons: need to add motor, glossy finish.
BOWSER
Pros: rides nice and low, near scale width.
Cons: too short, leading to narrow windows. Detail not that great (I added the retrievers).
I actually like all three but would give the top ranking to the Corgi, assuming the availability of motorized drives, because of the level of detail.