I have the Sena 10s in my shoei gt-air and Agv cords. It is easy to manipulate and works well with Siri on my iPhone. I have a Cardo Scala Q3 on the rf1200. It is not as easy to manipulate wearing gloves for me. But I feel the scala is louder as I can hear my pandora music my more clearly. One thing to look at is seeing if your helmet has cut outs for speakers. It makes things much easier.
Haven't upgraded my helmet in a while but looking at my X-11 it has room for speakers. The volume on the Sena Units aren't that great? I'd hate to get anything drowned it but normal riding (exhaust/ wind/ etc)
Well there are many variables. Type of helmet, hearing, type of bike/exhaust, ear plug/no ear plugs, placement of the speakers, etc. The sena 10s has a sound boost feature that helps. I would advise buying a system based on features and ease of use. Also on what your riding buddies use (Which is why I have sena and cardo).
I like both the sena an uclear cause of use with other systems. Don't really do much group riding, and if I do it's only with a handful of people tops. My needs are more in the volume and ease of use department, volume being the most important. I'd Rarely talk on it, but it'd be nice to be audible if I had to. Main concern would be the ability to hear GPS directions.