IMO the helmet protection band is fairly narrow within the possible outcomes from a fall or crash.

If we used the spectrum below as an example of all possible outcomes we might say that the green band is where the helmet makes a difference. The blues to the left represent those impacts where there would be little or no injury without a helmet, and the yellows and reds to the right impacts where the likely outcome is serious injury or death despite wearing a helmet.



Given that the band of protection is that narrow, small differences within that band are relatively less important. Keep in mind that bicycle helmets are designed with protection levels suitable for simple bicycle crashes, and not for crashes involving motor vehicles. So as a commuter, you face a reasonable likeliness that a crash will involve forces beyond the protection of any helmet.

This isn't to say that all helmets are equal, nor that wearing one is unjustified, but to offer some perspective so you may align your expectations to reality.