The best electronic muffs I've owned and tried are the Pro Ears Gold.
I have them, the Howard Leights, and the MSA Sordins.... the Pro Ears have the best cancellation, but still allow you to hear conversations. They don't cut in and out like some of the less expensive ones.
The Sordins work similarly, but I get a buzz/hum with them that I don't get with the Pro Ears Gold.