Stainless steel jingles are more shiny and the galvanized steel jingles are more dull in appearance.
The stainless steel jingles have more of a cleaner "jing" and the galvanized steel jingles have a tone plus a harder "clack" sound. Neither is better than the other, it all depends on the sound that you are wanting out of your chocalho.
Chocalhou jingles will wear out over time. After years of the jingles scraping over the bolts they will both begin to wear down. The holes in the jingles get bigger and bigger, and the bolts become thin. Go Samba also carries replacement bolts for your IVSOM chocalho. Link in photo below.