I personally love the 6 Key Holder. I bought one for my dad 8 years ago but he doesn't like it and I already have it hot stamped so I decided to use it. I have the Black Epi and it holds up very well, surviving being in my back pocket and having me sat on it for the past 4 years. It keeps all my keys in place so the key won't scratch up the inside of my bags (it fits inside my Petite Malle and that's my number one concern as I'm out and about with my PM a lot and the last thing I want is for my keys to scratch the lambskin interior of the bag). Secondly, it can hold up to 4 or 5 cards in its slot, making it extremely convenience for a gym run or quick trip out. And it's small enough that I can fit in any of my pants/jackets' pocket when I don't want to bring a bag with me.
I've used many cles many years before but I've decided against it because if you have 3 or 4 keys they will not fit comfortably inside the flat cles and if you keep the keys out, the combo of keys dangling out + pouch is too bulky for me.