using fbx im almost 100% that weighted bones work with a7 but that is a good point if unity does it on the gpu and a7 doesnt.

Everything here all boils down to this, use the engine that gets the job done, if you dont need decent shadows, use unity, make a drop shadow, or multiple ones (one per joint) or flatten a model. if you need decent shadows and you good at hlsl/working with script between the hlsl and the language your using, use a7, if you need to make a game with decent shadows and you have no hlsl/scripting expirience, go to school, or change your needs, or read tutorials for hours