The "easy open" mod changes the pivot point of the trigger guard hinge pin. The factory moves it from the front of the frame near the barrel hinge, to the middle of the frame(right over the trigger and under the cat). You may be able to see it in my pic above. I have never tried the standard, hard to open frame, so can't say how much easier it is to open. The previous owner sent it in and had it modded. I think he said it cost about $50.
This is from the TC site:
EASY OPEN CONTENDER FRAME CONVERSION
In 1981 T/C changed the location of the trigger guard pivot pin. The pin is now located toward the lower middle of the frame instead of up front, under the forend wood. This relocation was done to give the shooter more mechanical advantage when opening the Contender. We can convert any early Contender frame (before serial #195,000) to the easy open type. This conversion includes all the required parts (trigger guard, trigger, hammer, etc.) We will need the entire pistol returned to us.
Easy Open Contender Conversion - A23565 $55.95
Custom Shop - Accessories - Thompson/Center