I found power domes in the same ballpark as cShells, enough to let me appreciate the noise-reducing capabilities of the Spheres; cShells are the best! Keep in mind that you may need to use a different size power dome for each ear. Your ear canals may not be the same size. Your audiologist should be able to tell from your feedback profile how well the power domes are occluding your ear canals. With good low-frequency hearing, if you don’t have an occluded fit, noise will leak directly to your eardrums, and you won’t get the maximum benefit of Spheric noise reduction.
My cShells block external noise much more completely than power domes do. First, they are made to the shape of my ear canal, and second, the outer side of the cShells totally blocks the opening of each ear canal. I’m used to occlusion and insisted mine be made with no venting. They work great. YMMV if you’re sensitive to occlusion. Your HCP can adjust somewhat for occlusion in the Target app, and amplifying soft sounds in the MyPhonak app using the Dynamic sound slider helps overcome that (playing with the equalizer may help, too; haven’t analyzed my MyPhonak adjustments in detail, but I have custom programs that lessen occlusiveness relative to AutoSense; did not adjust for occlusion within Target).
A view of what cShells look like in their entirety is available in the following post: