Stainless Steel & Multi-Ply
Until the turn of the century (the 1999/2000 one), stainless steel cookware was to be avoided. Stainless (nickel / iron alloys) has very poor heat conductivity and the pans were thin because stainless is difficult to form. They were prone to nasty hot spots - fine for boiling water but not for much else.
That changed when All Clad perfected a way to sandwich
incompatible metals with a high temperature roller press (this may also
be done by explosive forming). Thin sheets of stainless with a core of
aluminum or copper solved both the heat distribution problems of
stainless and the toxicity problems of aluminum and copper.
Plain stainless is simply out of the picture today except for large stock pots where the ingredients will always be pretty much suspended in water, and for things like roasting pans where material is not particularly important.
Note that Stainless Steel comes in two general varieties - high nickel and high iron. If a magnet sticks to it, it's high iron, which is less corrosion resistant than high nickel. On the other hand, high iron is the only kind that will work on an induction range - though why anyone would buy one of those is totally beyond my understanding. Some multiplys are made with high nickel on the inside and high iron on the outside so they can be used on these ranges.
Multi-ply cookware is made in two designs. Slab: a plain stainless vessel with an aluminum slab welded to the bottom. Fully Clad: where the vessel is pressed from a multi-ply sheet, so the cross section is the same for the entire pan.
I've seen plenty of comparative reviews of sauté pans saying both designs work just fine - but they don't. Reviewers must fear a cut-off of free samples from manufacturers if they tell the truth.
Slab bottom pans are excellent for stew pots, stock pots and larger sauce pans where the bottom of the pan is much wider than the burner and the contents will always be pretty liquid.
The photo on the left above shows the construction of a cheaper pan with the edge of the aluminum slab exposed and ending quite far from the edge of the pan. The stainless bottom is very thin, but that isn't a problem. Despite it being a cheap pan, this 3 quart saucepan has given years of satisfactory service, because it is large and only been used with liquids and never for serious frying.
The photo on the right shows a more expensive construction (Cuisinart) with a thicker aluminum slab ending closer to the edge and completely encapsulated in stainless. This is a 2 quart sauté pan and it does exhibit a hot ring around the outside edge when frying, particularly noticeable with chopped onions. Generally the pan is quite usable, but takes extra care with stirring. A cheaper model made like the sauce pot in the previous paragraph might be a lot worse.
Slab bottom is not very good for smaller pans and particularly not good for sauté pans or skillets. I had a cheaper 1.5 quart sauce pan which was usable with liquids, but the handle was so heavy compared to the pan itself it tended to do a back flip off the stove if it didn't have much in it. It had to be replaced with a heavier Cuisinart fully clad model for safety.
Note that my 5 quart sauté pan is a good quality slab bottom (Cuisinart), and it works just fine. It's so much bigger than the burner the hot edge problem does not appear.
Fully clad pans are excellent as sauté pans, skillets and small pans. Chopped onions will brown much more evenly in such a pan than in a slab bottom pan but they are significantly more expensive.
The photo to the left shows the corner of a fully clad pan. It is a smooth curve from bottom to side and the pan is the same thickness at all points. The photo to the right shows the cross section, two very thin sheets of stainless with a thicker aluminum layer in between. Some pans have an inside ply of non-reactive 18/10 (alloy 316) stainless while the outside ply is a less corrosion resistant magnetic stainless so the pans will work on induction ranges (people who have those don't actually cook, do they?).
The fully clad design is not as good as the slab for large stew or stock pots where the bottom is much wider than the burner and the contents are more liquid. The aluminum layer of a fully clad pan is quite thin compared to a slab and has more limited heat spreading capacity. This can result in the center of the bottom getting too hot - particularly noticeable with soups containing barley and thick stews.
Some of the top names in fully clad cookware even make fully clad roasting pans. For roasting a turkey that's a total waste of money - but profitable for the manufacturer if they can get people to buy them.
Plain stainless once sold pretty well. It didn't dissolve in the food like aluminum, cost a lot less than enameled iron and was a lot lighter than either enameled or bare iron and didn't chip and rust through like enameled steel. The only problem was, it burned the food. Stainless steel has rather poor heat conductivity, so where it contacts flame or burner it gets plenty hot, and the heat doesn't spread out to cooler regions fast enough.
Revere Ware was an attempt to make stainless steel cook decently. It featured a thick electroplating of copper on the bottom, wrapping part way up the side. Revere Ware is still sold, but in 1968 they cut the thickness of the copper by nearly 50%, pretty much destroying its cooking properties. It's probably even thinner today. "Revere Ware" is now owned by World Kitchen, an accumulator of famous but distressed brand names.
Plain stainless is fine for roasting pans where the material makes little difference, and for restaurant size stock pots where the contents will always be very liquid. The photo shows my 20 quart stainless stock pot and it's basket insert (which is not stainless but chrome plated steel). I also have a matching 12 quart which is used to finish stews that have grown too large for my 8-quart slab bottom pot. If there is danger of things sticking to the bottom, I slide my steel comal under it to help spread the heat.Typical Pans
Multi-Ply Sauce Pans
Those shown in the photo are the ones I use, and at least one of them
is used every day. Lower left is a 1 quart Windsor and the upper right
is a 2 quart Windsor. Windsor pans have sloping sides which makes whisking
easier. That it's for more surface area for reducing sauces makes no
sense, the reduction comes from bubbling steam off the bottom. Lower
right is a 1.5 quart standard straight sided sauce pan. Upper left is a
3 quart no-name slab bottom sauce pan fitted with a steamer pan. All the
other pans are Cuisinart fully clad.
Multi-Ply Sauté Pans
I have three of these: a 2 quart, a 3-1/2 quart and a 5 quart. The
5 quart is slab bottom, but is so much bigger than the burner it works
fine for what I use it for, and at that size cost is a major issue. The
3-1/2 quart is the one that gets used constantly, the 2 quart less often
(and often to stand in for an already occupied sauce pan), and the 5
quart is the party workhorse.
At 13 inches this one is as small as is practical for a wok. Having a small flat at the bottom, it rests directly on burners for excellent heating, but the flat part is not large enough to interfere with regular wok function. Not needing a ring stand is a great convenience.
All Clad has a 14 inch one that sells for about 2015 US $199, which
is over $100 more than the Calphalon. At that price, I'm perfectly
willing to use my excellent Atlas 14 inch spin formed sheet steel wok
and a ring stand. All Clad calls theirs an "Open Stir Fry Pan" because
of the rather large flat area at the bottom.
Slab Bottom Stock Pot
I have a 5 quart no-name and an 8 quart Cuisinart, both of which are
used very often. If you routinely cook for a bunch of people a 12 quart
would be a good idea, As mentioned above I have a 12 quart and a 20 quart
in plain stainless, but I also have a 40 quart in bare steel, which I
haven't used in decades. The previous owner used it to store dog food,
but apparently the dog died and I got it at a yard sale for about $10.
Stainless and multi-ply cookware needs very little maintenance. Some pieces do pick up a bit of mineral deposits from the water and should be cleaned with hot vinegar now and then, particularly a wok because mineral deposits can cause stuff to stick to it.
Do not fear to clean this cookware with a kitchen cleanser like Comet or Pro Pride, but do not use abrasive pads or steel wool.
Other than that - just don't over-heat it. Temperatures should be kept down around 450°F/230°C. At temperatures much higher than that you risk delamination of the metal layers. If there's ginger in a badly burned pan it'll eat big pits into the stainless.