I'd use Silver. Bronze is OK, but bounces a bit too much for me. Gold is like Evil, you will have many breaks if your gun is rough on paint. Silver is mid-way between the two; the shells are thick but not too thick.
I like Inka Silver. I've used the white-filled "Feathered Serpent" one, and it was a pretty straight-shooting paint for the price. Though I'd recommend using one of the other Silvers, with a coloured fill. The white fill wasn't great.