The difference is in the amount of torque used to tighten the barrel down, Tom.
The older guns didn't use nearly as much torque. Jim is correct that you can often remove the barrels on the older guns with very little pressure.
The major problem with the new style is that there is no absolute reference to indicate when the barrel is screwed on straight. For years after dropping the cross pin S&W had problems getting the barrel screwed on so that the front sight was vertical. When I was working for the gun shop in the early 1990s we sent quite a few back to the factory that had front sight cants of 10 degrees, or worse.
"The gift which I am sending you is called a dog, and is in fact the most precious and valuable possession of mankind" -Theodorus Gaza
Baby Jesus cries when the fat redneck doesn't have military-grade firepower.