In the early days it was brass but those clips were a right pain so i swiched to S/S. 
Now i'm a pro window cleaner so i use my pole 
Make your mind up Macc, one or the other.

Brass is great, it looks so nice.
You don't need brass clips, just use the plastic Unger ones.
Or do what I do, and don't use any.
It keeps the edge of the squeegee into the edges of the glass, and retracts in a bit if you push in too hard. Magic.
