I find that my 4-week-old will calm down differently for me vs my wife. My theory is that my wife smells like milk, so if he's hungry, nothing but mom will do. Other times, he can get agitated if mom is holding him but not feeding him - but he has no expectation of food from me, so he'll be calm for me.
His older brother, now two years old, used to calm down for me but not his mom, long after he was weaned. My theory there was that he knew that dad meant business, and that no amount of squirming was going to get him out of being rocked to sleep. Mom just doesn't have the stamina and strength. It took about a week and a half or two weeks to get him used to the fact that squirming with dad was pointless - and then many months of that before mom could really do anything (once he had learned to calm down and sleep). Six months later, and he finally is more or less going to sleep on his own.