I don't have a preference in regards to nickle or brass. I like Golden Saber and it happens to be nickle plated. I have never had a hiccup with my p89 and I have shoot just about every type of cheap ammo through it.

I use brass fmj in my lcp because I want a bit more penetration with the lighter bullet, I have no favorite so right now I think it is loaded with Federal.

I have nickle plated Winchester Silver Tips in my .38 because it was a good deal on an older box.