My wife and I both use the custom molded plugs also. We've never used electronic muffs so I can't say how they stack up, but the custom plugs, in my opinion, are better than using the foamies along with regular muffs. I've shot on the pistol side standing next to guys shooting comped open guns with no issues. They are a bit more costly, but they are comfortable and effective. Another big plus is that they guy that makes them is a really cool local guy from Maui. We bought ours when he first came down to gun show the other year, and have no regrets at all. He explained the whole process, what he was doing each step, and just was a real pleasure to purchase these products from. He also can make molds which can be sent away to make the custom hard material plugs which can accomodate electronics (ipod speakers, communications, etc), something akin to what NASCAR racers use. My wife and I will probably try to catch him at the next gun show to get those made next.
Excellent product, excellent customer service, from a local vendor. In my opinion, not much more one can ask for.