I'm just pointing out a few things that I've discovered while researching and listening to others. TO be clear, the only hands on I have is with a Sena 20s. Everything else is from hearsay and online documentation.
In the Cardo camp I've heard from many that have tried both the Cardo and the Sena that the sound and connections are better with the Cardo.
I'm also told that the Cardo voice commands work much much better too. Judging by how poorly my Sena 20s performs in that area I don't see how anybody could
make a unit that works worse. I respect the people whose opinions I have received and thus I do believe the Cardo over all is a better unit.
So based on those reports I started researching Cardo mesh units. One thing my Sena 20S does, and the Sena 50s does as well, is have a speaker connection as well as an ear bud connection. From my research Cardo is either/or not both. You can plug in ear buds or helmet speakers not both. My modular helmet is noisy and the best way for me to shut it up is to use ear buds which plug in easily and shuts off the speakers. However sometimes for just short hops I don't bother with ear buds, for instance after a long day of riding I go to the hotel and shower then ride to a local restaurant that isn't in walking distance. I still want to hear my riding buddy tell me that I made a wrong turn or that he did while we are headed to the restaurant but I'm done with ear buds for the day. The Sena works great for this scenario, The Cardo would require me to plug in the speakers before doing so. How difficult is that?..I have no idea, but would it have killed them to just have the speakers connected all the time and added an extra plug in jack for ear buds? Not a factor for many but a feature I want. The second thing or feature the Sena units have that the Cardo units do not is an external mic that allows you to hear what's going on around you even with ear buds firmly in place. Whether its just someone walking up to me at the gas pumps or interchanging info with a store clerk I frequently use the external mic on the Sena. I rarely remove my helmet at gas/bathroom breaks so the external mic really comes in handy. The external mic seems to be co-located with the USB jack and I think it may be the main reason that the Sena is only water resistant and not waterproof like the Cardo unit is.
Anyway, despite my thinking that the Cardo is a better built unit (and reportedly better customer service) I'm sticking with Sena for now just because of the 2 features the Sena units have that I frequently use and would miss (but mostly for the external mic).
I doubt many care about those features except me, but I thought I'd point them out just in a rare case there are others that may like them and might be disappointed when they purchase a Cardo and find out it doesn't have them. Again probably not factors for most