@AlbertoT I think what he meant was that shaders have good fallbacks to older hardware. So you can have your game with shaders, and if somebody plays it with a pc that doesn't support those specific shaders it will fall back to an older version of the shaders that the pc supports.
It is a matter fact that Unity3d game engine is well optimized
I tested Unity, dxstudio, Leadwerks
Even though I would prefer Leadewerks workflow over DXSTUDIO and DXSTUDIO workflow over Unity I finally went for unity, Unity being much faster on modern PC
However i doubt that , generally speaking,Unity can be faster than 3dgs on old PC'a unless , as you said, he was talking about shaders only
