Just a guess on my part, but I believe the PM4 is going to be louder. Just from reading their specs and such on their site ,the fact that they give you a db rating on the PM4 tells me they are proud of the sound. Ive seen some posts around that ask how to amplify the PM3. Id like to think Johnny Stewart took that into consideration along with the wireless side. Unfortunately, this is a very new product, so there may be very very few out in use at this point, unless there are some insiders on this site.