I haven't used the Sena helmet, but I'm currently reviewing the Coros SmartSound Urban helmet. The features between the helmets look pretty similar although the Sena is cheaper and doesn't have an integrated light or SOS feature.

Riding with the Coros smart helmet has been pretty cool though. Typically I play music through my cellphone, but with these smart helmets you get more directed audio and additional features. I'd recommend taking a look at the Livall smart helmets as well, which include turn signals and larger integrated taillights.