The custom molded earplugs are more comfprtable and do block a bit more noise. (i think they rate around 32-34db)
I've had a few sets made, mainly for motorcycling. I really liked them while they lasted, but after paying the extra cost and losing them after a bit; I just went back to the yellow foam cheapies.
If you are a little more diligent than me, and can keep from losing them, they work great
NRA Life Member, SAF contributor.