Water chiller question

This is my first post so bare with me. I want to use a water chiller to cool my nutrients.
The plan is to use a cooling coil submerged in the res. The easy option would to use a copper coil but what about stainless steel. Its more expensive but is it better? whats the pros and cons to each?
thanks to anyone who can answer this.

just in case anyone cares i made a coil out of SS rod and coiled it. if any one wants pics let me know and ill post um.
the reason i didnt use copper was because i heard it can throw off ph balance.