To provide an example I just produced a pair of shots at f5.6, one with my A50/1.2 + tube and the next with my A50/2.8 macro lens
I can't help but feel that the quality of the two pictures presented are somewhat exaggerated given that you're comparing a dedicated 50mm macro lens vs a 50mm f/1.2 lens. I suspect that you'd see much less difference with the far more commonly used 50mm f/1.7 or f/2 lens.
Godfrey
