I bought two pairs, and this is my experience:
Loop Experience - the noise reduction is very subtle. Only when you take the earplugs out you notice that everything around is louder than with the earplugs. The sound quality is excellent - what gets through the earplugs sounds absolutely natural to the extent that you hardly notice the effect. Talking to people takes more concentration, though, because of the lower volume.
Loop Quiet - the noise reduction is much less than I hoped for, I am a bit disappointed. Even with the Quiet earplugs in your ears, you hear quite a lot. I would say that they are closer to the Experience level of noise reduction than to the foam earplugs you get in every drugstore. If those foam things achieve 30dB or more of reduction, then Loop Quiet would be half way between that and the 20dB advertised for Experience. So don't expect real quiet with Quiet. If you really need silence around you, use foam earplugs.
The good thing is: Both sets of earplugs are very comfortable, once in place you all but forget them. And they are easy to use - just plug them in and you have the effect immediately. They are easy to remove as well, but I've never lost one. The little pouches are pretty useful, too.
Soul Bordeaux