Oh boy... there's some great threads on 2+2 that discuss ALL the facets of different cards, rating them for stiffness, flexibility, feel, thickness, etc...
OK, found the thread on 2plus2. It's long, but has some amazing analysis of the different cards out there, and ranks the cards in order, based on their performance in each category. Ooo, and there's pics too
Playing Card Roundup
I'll add that this thread was started in 2011, and that cards (and the thread) have updated along the way. One post starts by raving about the KEMs, however, I believe KEM underwent some management/ownership issues, that translated into QC issues for many of their beloved cards.