Just as is the case with "impact vests" there is a bit of speculation as to the different possibilities in an accident. There really isn't any research or testing regarding vests and whether thicker padding will be better or worse when a fall impacts your ribs. Same goes with handle guards, except to say that if your head gets fully into the triangle in it is almost 100% fatal. So ANYTHING that keeps your head from getting fully into the triangle is better than nothing. We do have one documented situation where there was a handle guard and the handle still caught his chin and caused damage needing a long recovery. This can likely be minimized by a stiffer guard, so if your head hits the harder plastic guard it will minimize the chances of the handle grabbing the chin.
Then there are arguments that if your arm gets in a guard may prevent it from coming out, or that a rubber coating may minimize damage etc, but less space for your hand to get in may prevent the arm from getting in in the 1st place. All of that is pretty much speculation and theory, so for one person to say it is that way has to be taken with a grain of salt..... ANYTHING is better than nothing, again pretty much preventing the head from getting in and almost definite fatal results. I feel less space for an arm to get in the better, and agree that a firmer plastic to minimize the chin getting caught on the bar is better also. But again....all is just theory.