12051 has a Vistadome coach. The Vistadome coach has an observation area on one side where one can stand and watch the view. In 12051 the Vistadome coach is the last coach and therefore there is clear view of the rail track and the scenery from the observation area. However, in 12052 the vistadome coach is immediately after the loco therefore the observation area does not offer any view other than the back of the loco. Therefore, if you decide to travel by the Vistadome coach, it makes sense to book by 12051 rather than 12052