Hi Murray:
I only have a handful of exotic holsters. I'm trying to learn more about exotic skins. But everything is relative.
The two most common exotics that you see today used in holsters are shark and ostrich. Both are very abrasion resistant--more so than cow or horse hide. A sharkskin holster is water resistant and can last a lifetime. But ostrich can be dyed and is more flexable cosmetically, yet its abrasion resistance made it popular with boot makers. Both are readily available and easy to work with.
Snake skin use to be more popular, but it has fallen from favor because is is very delicate. It is used more for its beauty than any practical reason.
The toughest leather for both abrasion and mosture resistance (that is commonly used for holsters) is ray skin, but it is very, very difficult to work with; there are over 200 different kinds of "ray;" and, the skins tend to be small and very expensive.
Lizard is more durable than snake, but less so than shark. The problem with lizard is that there are a lot of different lizards, each with their own considerations. Lizard is replacing snake because it is more durable and the skins can be very dramatic in appearance.
Elephant is now available, it is durable but like most land critters it is less mosture resistant than ocean critters.
So the bottom line--buy what you like. You will never be disappointed with shark or ostrich. Both wear like iron. Lizard can be dramatic and the texture and grain patten can take your breath away. Elephant is so novel that you will spend more time passing it around than wearing it. A great gun club ice breaker.
By the way, most exotics are bonded (glued) to either cow or horsehide.