The minute I saw the magnetic clasp on the Sena model, I was hooked. I'm not a fan of the extra flap.
Mind you, haven't actually seen one up close I can't say how good it will be.
At the end of the day, I want a case that will envelop and enclose my 8700.
I'm not a fan of the removal type as continual removal will eventually and inevitably scratch or mar the unit. That was the case with one I had for my other Blackberry and my other phones.
For me Sena might have the right answer.
Once they ship and I get mine, we'll see how well it actually works.