It really is in your best interest to wear both. One of the benefits of wearing both beyond the additional protection of using doubled hearing protection is that the plugs will do a good job of protecting your hearing if and when the muffs you are wearing get knocked askew. This sometimes happens when the shooter's muffs bump the stock of the long gun when getting a cheek weld or during recoil if the stock contacts the muffs.
You should consider going with one of the thinner electronic muffs. The large or bulbous muffs tend to suffer getting hit on the stock much more often than thinner muffs that don't protrude out so far from your head. Unfortunately, the thinner muffs usually don't or can't offer as high of an nrr rating as some thicker muffs. For example, some of the thicker passive muffs may offer protection up to around 33db of noise reduction. Thinner muffs like thinner electronic muffs may only provide 16-20 db nrr. There may be exceptions, but they are probably much more expensive.
So if you go with the thinner electronic muffs, you need to get the higher rated plugs. Plugs are cheap and you can get plugs providing 30 or more db reduction.
One of the problems of using plugs and muffs together is that there is so much noise reduction that it can be difficult to hear what others are saying and almost impossible if the voices coincide with loud noises. By comparison, it can be hard for a person with hearing loss to be able to follow/hear a conversation when there is a lot of background noise, such as at ranges, dance halls, or around loud machinery....to name a few comparisons.
To overcome this aspect, what makes doubling up so cool with electronic muffs is that you can turn up the volume on the electronic muffs to actually increase the sound broadcast through the muff. So the extra volume of normal sounds such as voices can help offset some of the nrr provided by the plugs. So things like regular voices can make it into the ear at levels approaching normal conversation levels. Of course when the electronic muffs shut down the broadcast due to a loud noise, the loud noise is reduced through the muff and then through the plug, providing greater protection than the muff or plug alone.
I have Pelto Comtacs that are a mid thickness electronic muff. To overcome the plugs, I have to have the volume of the muffs turned up fully to adequately hear conversations. With sounds broadcast that loudly by the muff, if you aren't wearing plugs, then you probably don't want the volume turned up so high. I haven't verified how loud the broadcast is, but I suspect it is enough to cause hearing damage. Prolonged amplified sound when turned up high can become uncomfortable after a while. That indicates the sound is more than you should be wanting to experience.
Electronic muffs with the volume turned up high and not wearing plugs can be beneficial in many situations where there isn't much sound. Through the ampiflication of sound in environments where there isn't much noise, you get to experience something akin to having a bionic ear. You get super hearing. The Walker game ear is based on super hearing to help you detect sounds in the woods that are too soft to hear with your regular ears.
For example, with the house dark and wearing muffs on full volume, I can essentially clear my home audibly. I can locate walls based on the few sounds in the house when the house is quiet. The quiet sounds are reflected by the walls and so when facing a wall, the sounds heard are louder than when facing away from it. I can walk into a room, or just to the door and determine if my kid is in bed as I can hear the kid's soft breathing. Normally, the sound of the breating would be so soft that I would not be able to hear it unless very close to the kid, say within five feet. Similarly if there was an intruder in my home and hiding, unless that intruder knows to significantly mute the sound of his own breathing, I can tell he is in the room.
In other words, it is like using the muffs as a form of passive sonar.
Cool stuff.
