I used to use the old Sonic Ear Valves when skeet shooting, and they worked reasonably well but were never particularly comfortable and I always ended up with sore ears (not from noise, but from the plugs themselves) after an hour or so. The same thing is currently sold as Sonic Valve II and it looks like they may have improved the comfort factor a bit. One problem is that they only have an NRR of 18, which is pretty low compared to even cheap electronic muffs, and way below the NRR of 30 or more that the better foam plugs achieve.
The OP is asking about CUSTOM MADE earplugs not off-the-shelf Sonic Valves. There is no comparison.
I'm not sure of the custom plugs you're referencing. I have a pair of
"Chameleon Ears" made by E.A.R., Inc. that have a passive, impulse filter. They have a noise reduction rating of -32 dB to -33 dB.
They need to be custom fitted - don't try and do it yourself. I paid $145 for the ear plugs with the custom fitting. E.A.R. returns the molds so that you can have additional earplugs made from the molds - so it is really a one-time cost. If you contact E.A.R. they will put you in contact with a local dealer that can make the molds.
You can hear range commands and voices, but they are not like a pair of electronic earplugs. A pair of electronic earplugs that provide -32 dB of protection can cost from $400 to nearly $4,000 depending upon the sophistication of the amplifier circuit and whether they are custom molded or not.
Here's a link to
E.A.R. website where you can look at a variety of molded ear plugs with electronic amplification.
Custom made plugs are far superior to any other type of ear plug noise protection as they fit from the interior of the ear canal to the outer ear area. The plugs fill part of the outer ear area (concha cavum), and that cuts down on bone sound conduction to the inner ear.
You can hear and feel the difference between foam plugs, or any type of simple ear canal plug and the molded plug with the outer ear protection.