Freedom Arms is the only gun company I know of that has embraced the use of reloads, and supplied me with printed reloading data.
I'm 54 years old, and I do not recall ever seeing LEOs putting cartridges in leather loops on a cartridge belt. They always carried ammo in speedloaders in pouches, so I'm not really a believer in the nickel/leather explanation. Maybe the pouches were leather too, but I know that I prefer nickel for defensive revolver ammo because it tarnishes badly just from handling it with your fingers.
I'm also one of those who documents how many times my brass has been reloaded, and I'm also one who has noticed no difference in the reloading lifespan, at least with 357 and 38s. I've not come across 9mm nickel, but it would sure be easier to spot on the ground.
My advice, if you have it, use it, and draw your own conclusions.