Hi. Maybe I can help clarify some of the info from those article GotGarlic posted. (Both of the serious eats articles have some good information, but perhaps draw some misguided opinions from them. A little knowledge not well understood can lead down the wrong path)
Question 1. Browning in cast iron and stainless.
Steel is a moderate heat conductor, whether stainless or cast iron. Both similar, not amazing, but gets the job done. The biggest difference is their heat capacity. Cast iron pans are a lot of mass and as such can absorb a lot of energy. Stainless are thin and can not hold much energy. This means you need heat up a cast iron pan for several minutes before the whole pan is evenly hot, whether as a thin stainless pan is evenly hot quickly, seconds. At this point the pans may be at the same temperature, but the cast iron is holding a lot more energy... a LOT more, those several extra minutes more of heat getting absorbed. Think of it like a stock pot of boiling water versus a shot glass of boiling water, both are boiling, but there is just so much more hot water in the stock pot.
If you put a steak on both of these pans, the cast iron just has so much more heat energy stored that it can transfer to the steak than the thin stainless pan. The cast iron will "sear" the steak by adding a lot of heat very quickly. The stainless does this too, by with a lot less stored heat and thus a minimal, if even noticable "sear". However, when both pans have given all their stored heat to the steak, the are still getting new heat from the burner.
This new heat is also transferred to the steak, although slower as the heat conduction of both stainless and cast iron is only moderate. Over time the pans will both transfer heat into the steaks. Assuming the burner is hot enough, both steaks will undergo the high heat chemical reaction that causes browning.
So in conclusion, both pans will brown the steaks. Stainless a bit slower to start, but still works. Cast iron very fast at the start, causes noticable searing.
(Should be noted that more expensive stainless steel pans are often made of a sandwich layer of stainless steel on the top and bottom with a middle layer of aluminium or copper. This helps with even heating and improving the only moderate heat transfer of stainless steel with the significantly better performance of copper or aluminium)
Question 2. Cleaning a cast iron pan (?)
Cast iron pans are usually low cost, you can get them old and used often cheap. If they are rusted and the season is very damaged, you can give them a good INITIAL clean. Use whatever NOT corrosive cleaner or scrubber you want. You will have to reseason the pan though. The unsaturated oil /fat season procedure in the article works fine. (Though I would repeat it several more times personally.) If the season is not badly damaged, I would not soak the pan. Use some dish soap, a cloth and warm water to wash the rust off and then reseason the pan a few times to repair the season.
Cast iron reacts easily to many chemicals and even the oxygen in the air. The season coats the pan to protect it from the air and anything else it might react with. Be sure to use the oven season method at least once while the whole pan, top, bottom, and handle have some oil to season the whole pan to protect it. Just like rust under the paint of your car chips the paint off, so too will rust forming under the season of the pan.
Once a pan is well seasoned, it should resist (resist only) damage from soap and water. Soap actual bonds to oil and fats, so any free oils not altered in the seasoning process will be removed. Not actually helpful to maintain a good season. If you must use soap and water, dry it on the burner to prevent rusting and wipe it with a thin film of oil top, bottom, handle, the whole pan. Rust is the enemy. With a good season, you can often just wipe clean the pan once cooled.
(Use cast irons for cooking with oil. Try not to use them for cooking with water based liquids. Water and heat can damage the season. Acidic liquids WILL damage the season.)
Question 3. Flat versus ribbed pans.
Honestly, I think this is more about preference. Flat is versatile and can be used for anything fried. Ribbed is more for steaks, it gives those grilled sear lines on steaks, but makes the pan harder to use for other cooking when you would stir something. Personal preference. You spoke of steaks, so if that is your purpose, then maybe you would like the sear grill lines? Otherwise flat is more useful... and common, I rarely see those ribbed pans.
Question 4. Enamel versus seasoned.
Again this is mostly about preference. Seasoning or enamel, both protect the cast iron from rusting. Season can be restored and built up over years of use, but must be maintained and kept out of water. Enameled can be soaked in water, and scrubbed if required (only if really, really required, I would hate to damage an enamel pan), but they never develop a non stick season.
Enamel that is durable is not easy to make. Cast iron grows and shrink a lot when heating and cooling, all metal does. Cast iron enameled pans need the enamel and the cast iron pan to grow and shrink the same amount at the same temperature. Requires some detailed material science to develope and create compatible materials. Adds to the cost, a lot, remember cast iron is very low cost.
I hope this helps you choose the pan you need.
One last note relating to GotGarlic query about acidic food.
Rust is the enemy to the season of the cast iron. Acidic food would also damage the season. This is why to avoid acidic food. I suspect that the concern about iron in the food is a presumed or assumed risk, and hence a reasonable proposition as to why to avoid acidic food. The problem of a little knowledge without understanding. The true reason is the damage to the season of the pan.
True there are medical conditions requiring low or no iron diets, but in general iron is necessary for the body and is a part of many foods. Our bodies oxygenated red blood cells are red because they are partly rust, iron and oxygen.
