Difference between 3&5

My wifey told me that the 5-hole block ~1974 is considered strongest. One indication is that the front web on the L side is thicker. But, I haven't heard of 3-hole blocks failing, other than when a rod comes thru the side which might happen to any of them. So, best to use the "correct" one for your year.
Should I make a joke about the pillow-talk your wifey told me?