With the MM ones, essentially at all times the entire weight of the front of the car is being held up by the little bit of washer overhanging on the 4 bolts of those center plates...
I dont see it being a stronger design, because its weakest link is exactly what I just pointed out.
As a mechanical engineer I can tell you the MM are stronger just looking at the design compared to Granetelli unit. Note the spead of the bolt pattern, thicker web section where the holes are drilled and all steel construction.
The spread may be better, the material may be better, but bottom line is when the front slams back down every bit of that design is relying on only the strength of the 4 washers overlap and the little tiny bit of bolt that might be hanging over as well.
But the actual shock/strut/tire sidewall takes away alot of the impact anyway.