I just got a Freecom 4 from Scala/cardo myself. I haven't even had it on a 30 minute ride yet so no idea how I like it, but at home on the couch, it works great.
I will say that the button functions listed on their website don't match what I have to do to skip forward, backward or pause my music when its playing. Per Cardo, 1 press will play or pause. For me, if its already playing, 1 press skips ahead. 3 clicks should backtrack, but on for me, its only 2 clicks. Newest firmware and all. I think they messed up somewhere.
If I ever try a Sena, I'll let you know.