Here's a picture of 50B.

https://images.app.goo.gl/D7xtuy4AZpaFoqsK9

As there's no seat in front of it, in theory you can stretch out further. However, as you can see the footstool has a surround (the barrier) that makes that difficult in practice.

It makes little difference unless you are particularly tall - the main benefit of the seats mentioned is that no-one will be climbing over your legs