Classic propane turkey fryers come in 2 different metals-stainless steel or aluminum. They both have good points, they both have not so good points.
First and foremost stainless steel is easier to clean than aluminum. Aluminum must be cleaned right away. It will pit and get a sticky layer of residue on it that is hard to get rid of. Stainless stock pots and patio stoves will usually clean up with soap, water, and a sponge. The bottom of the aluminum pots are much harder to get the black soot from the LP gas off of as well. There is a lot more elbow grease involved when it comes to the aluminum turkey fryers. There is an oxidation factor over time that will cause the aluminum to take on a graying color. That will not happen with the steel.
Secondly, an aluminum stock pot is a better heat conductor than a stainless one. That means your frying oil will heat quicker. There is a reason that some stainless steel pots are made with copper bottoms. Copper is a better heat conductor than many other metals. It helps to more evenly distribute the heat in a stainless steel pan. The conductivity of copper is among the highest, stainless steel one of the lowest, with aluminum somewhere in between. (The aluminum pot will also cool down quicker after cooking).
Last but not least. Cost is a factor. Stainless steel is much more expensive than aluminum. (This is probably why they don’t make stainless steel fryer pots with copper bottoms). It is also heavier than aluminum, so if you are having it shipped, again cost may be a factor. If this is your first time around with a turkey fryer, the cost of aluminum may be the way to go. You may not like the process.
You may decide that this is not for you. Should that be the case, there is not a lot of money lost, and you can probably resell it quite easily. On the other hand, you may love it and decide to fry everything in the house. Then you may go on to use your pot for other things, like backyard New England clam bakes, or chili for a tailgate party. If that is the case, you may want to have an aluminum fryer as a starter fryer, and eventually move on to a healthy relationship with a beautiful shiny stainless steel fryer.
So, stainless steel or aluminum? No matter which metal you decide to go with for your outdoor propane deep fryer pot, as long as they are cared for properly, both will last you a life time.