Any padding (that is, not perfectly rigid material) you put btw foot and ground will make you a little bit slower, because it will slow the foot on it's way to point of return, some energy will be lost on deformation, compressing that material ... So, in conclusion, wearing shoes will make your legs slower, and hit the ground with less force than barefoot.
For a balance, if that material is elastic, it will conserve some of energy that would be dissipated on hitting the ground barefoot, as well as some of the energy put in to deform it and it will return some of conserved energy while expanding. In any case, less energy will be output than input, but it will possibly be more output than barefoot.
Also, there is some added mass, which will additionally decrease leg speed, but on another hand will help produce more energy by putting greater force into ground.
Then, it is not only how much it will give back, but also how long it will take.
Best case is spring to both compress as slow as possible and expand as fast as possible, all within natural time frame of one step. That is, be as stiff/ soft as convenient.
Softer they are, faster/ easier they can compress and slower they expand.
And vice versa.
So, where's the real benefit of wearing shoes, then, except in protection?
It is in friction. Basically, more grip, more muscle force translated into propelling, useful energy.
Speaking of grip, what someone have said, that he was wet from water flying of vapors running in front of him, is possibly much more important than all this bouncing thing.