The VW group, which currently owns Bentley, is the only automotive group in the world that makes engines in a “W” configuration. This video tries to answer the question of why it’s preferred over a traditional V12.
First advantage would be packaging, as a W is shorter than V, and it can be set further back in the car to balance the weight distribution. This is the case for the Bentley brand, but it has obvious roots in VW’s renowned VR6 units.
Another would be ease of manufacturing and development – it would have arguably been more difficult to engineer a completely new V12, when VW didn’t make any conventional V6 units of its own.
It also makes all the cars it equips more unique, different from the competition. Some will still prefer the traditional approach more, especially since a W12 does not sound as evocative as a V12, as the XCar video posted below tries to explain in more detail.