Re: Nickel plated brass??
I asked this awhile back as I didn't know either. Some felt that the plating would flake off, some said it actually held debris and scratched their dies. Others said they saw no difference, so I got some and tried it. So far I have not noticed any difference as far as strength, stretching, flaking, ect. I do like the fact they never tarnish or look bad. So for me at least so far the only con has been the slightly higher price.
I by no means use it exclusively but have in a couple different cartridges. Sorry for the limited experience but thought I'd throw it out there.