it's the frequency of noise that they block that seems to be the defining factor - I used a similar plug last week that higher rated (32db) and was pretty ineffective but it was a 'snore blocker', whereas the ones I bought that were 27db were industrial so perhaps they are designed to block differe t frequencies.
I've been using the earpeace motor sports plugs for a year or so as well. They are very comfortable, make a reliable seal and have three inserts for different sound attenuation. I've had custom plugs made but they were never comfortable. By far the best earplugs I've had and they are pretty inexpensive.
These work great for me. I'm sure a lot depends on your ears and the helmet in terms of fit and comfort. I did not use the wire because it has a metal part that pressed against my ear when helmet was worn. Instead I used the tab. The other great thing is the case can be put on as a key chain so I never lose the earplugs.