What material are good for mashing/boiling. I think stainless steel and copper are good, what about aluminum and enamel?
Both are fine, my pans are all aluminum as Stainless on that size is hard to find and expensive over here.
If you would cook on it you can brew on it.
Just be careful with what you use to clean them, John Palmer has some tips
I also want to share some points,
Both Stainless steel and copper have good conductivity, copper have some what higher heat conduction. On other hand stainless steel have long life and stainless steel also have good corrosion resistance.
So during CIP (Acid and base solution cleaning) of kettle stainless steel shows good response. Now days majority food grade equipments are of stainless steel.
One more point, Stainless steel is more stronger than than copper. ( More Water chloride contain is the drawback of stainless steel)
Main important point is cost, definitely stainless steel will be cheaper than copper.