On the nerdy side of things As discussed, aluminum is a lot more reactive than stainless in certain environments, and thus can oxidize and/or pit and cause poor outcomes for things like syrup. Aluminum also has a much lower melting point and becomes soft at much lower temperatures, and with some folks using forced air and gas and oil, long days of boiling at high temps can cause the aluminum to fatigue much quicker. For larger pans, the stainless steel is stronger than aluminum (although, as the airline industry will attest, aluminum has a much better strength-weight ratio, but we aren't really worried about that) and is thus less likely to deform when it gets hot with those forced air systems, etc. If you want a great radiator to distribute heat quickly and keep your sugar house from burning down, use aluminum. If you want a physically strong and chemically stable material to make high quality syrup, use stainless steel.

Now, if someone could invent a water jacket system (not copper coils) to sheath our arches and stacks to preheat the incoming concentrate...