For many years, S&W fitted their barrels rather loosely and kept them from unscrewing by using a cross pin.
Actually, the fitting is the same. The pin was there to keep the barrel from coming completely off if the threads got stripped somehow.
Neither approach is better; the company simply moved towards a more efficient approach. The same goes for not counterboring chambers any more--it wasn't necessary, and it just added to the cost.
There really isn't any difference in function, accuracy, or durability.