Sorry, I need to meet a pro optometrist!
What I like in piezo is the versatility, but it also means quite a lot of adjustments. Wide frequency range gives possibilities, but there's that extra hassle. I think that two outputs and two preamps would be the ultimate solution, but who wants to carry all equipment to the gig, I don't know.
All in all, Affirma is a different instrument if you are after something else and want to experiment.