You certainly want to go with the stainless one. It doesn't take much of a lapse on maintaining pool chemistry to have the water eat copper. Certainly that neglect you see in a "closed" pool will do it.
I agree with Greg that I would use the SS one myself. It looks like these connections goes right onto the hoses from the pool filter, skimmer or return. I wonder if they will catch debris and clog up the line?