A S&W hammer block can break just as easily as a Ruger transfer bar, so both designs are roughly equal in that regard.
God forgive me, I am going to throw gasoline on the fire.
I have read more
incidents of Ruger transfer bars breaking than S&W hammer blocks breaking. As a matter of fact, when I routinely peruse the gun smithing forums, I have seen several instances of Ruger transfer-bar failures but I do not remember any
instances of S&W hammer blocks failing. So, that would seem to indicate that both designs are not, "...equal in that regard..." Unless you want to blame it on the part and not the design, that is.