[showgun410]

I'm looking to buy a wort chiller for my 7.5 SS brew pot, is a copper or SS wort chiller better?

[anje]

Copper's the material of choice. Better heat exchange and the yeast appreciate a few extra copper ions, as I understand it. I suspect it's more prone to damage, should it get smashed behind something, but can't say I've actually made the comparison.

[hopfenundmalz]

If you run the equations for a heat exchanger in a liquid to liquid situation like we have, the SS comes out to be about 89% effective when compared to the copper chiller IIRC.

Edit - everything is the same, just change the material properties of the chiller.

[beerbrewinwizard]

Just remember to drain "all' the water out out of it if you live in an area where it freezes. Ruined one like this when I forgot to drain it. I got in the habit of storing it up-side-down so it will always drain. Yeah, copper works better given the same amount of surface area and mass.

[redbeerman]

Copper is also easier to work with.  As always, design is all about compromise.

[kramerog]

I'm assuming you are talking about buying an immersion cooler.  I think the benefits of higher heat conductivity is greatly overstated since most of your heat transfer resistance comes from the lack of circulation of wort.  I would go with the cheaper cooler all other things being equal.