Hi Don,
If you hold the sporas by the back of the heel, it is quite soft and bends underneath the foot for a little less than an inch forward, the soft part extends about a total of 1.3 inches forward from the bottom of the heel. The rest of the underneath part of the pocket is rock solid. By comparison, the cressi's bend when held for about 2 inches forward of the bottom of the heel and the bottom of the pocket is fairly soft for 4 or 5 inches forward. The top of the pockets are also different, each has a band of stiff material in the center, with softer material near the toes and ankles, but the stiff band is about 50 percent wider on the sporas. In the water, it feels like better power transfer across the top of the foot. I can't really feel much difference underneath the foot.
Overall, a much stiffer pocket on the sporas, enough so I was a little worried about wearing the sporas barefoot for long periods. However, pool workouts are building caluses in the right places, I think summer is going to be fine. Now will the wind please die! NOW.
Connor