Baking – What size pan should I use if I want to split a recipe in half that calls for a 13×9 inch pan

What is the advantage of a steel skillet over a cast iron one? I currently use cast iron for most everything and am curious what I might be missing.

Pan sauces made with wine, vinegar, or any other acid are better in stainless steel. If you put any acid in cast-iron, you are harming your seasoning, and leeching iron into your food. This will affect the taste of your sauces, I find pan sauces taste metallic when made in cast iron.

Stainless steel also heats up and cools down much faster than cast-iron. This is great when you need quick heat, or fine control of your heat. You can also plunge a piping hot stainless pan into an ice-bath without cracking it in half.

If there's an advantage to getting a steel skillet as well, what would be recommended?

Go with a a bonded stainless-steel pan with an aluminum core. The most well known manufacturer is All-Clad. The stainless steel exterior is great due to it's non reactivity, you can literally put anything in it. The aluminum core distributes the heat much more quickly and evenly, minimizing hot-spots.

Is a steel skillet good for cooking omelettes?

Not in my opinion. I go with a non-stick pan every time.

I have to recommend sticking with a nonstick pan for eggs. There's simply nothing better, although well seasoned cast iron comes awful close. If you're spending more than $20 for a nonstick egg pan, you're doing it wrong. You don't need Calphalon, or any other big name for a good nonstick pan. Go to a restaurant supply store if you can and buy a cheap one there. With care it should last you 2-5 years depending on use. I found my current one at a Bed Bath & Beyond.

I suggest getting a quality stainless clad saute pan or saucier. For years I made risotto in the All-Clad 3 qt. saute pan shown here:

Unless you're serving huge portions this is plenty of room for 6 servings of risotto. There are larger options available though, including a mammoth 14" 6 quart one.

This pan easily does 90% of the work in my kitchen, so at any price it carries its weight in the kitchen.

That said, this past Christmas I got the All-Clad 3 qt. copper-core saucier shown here:

It's a very close matchup, but this pan is perfect for making risotto. The higher sides are a definite benefit, but you don't sacrifice much in flat surface area. The copper core is amazingly responsive, noticeably more so than aluminum. It's obviously rather expensive, so if you're uncomfortable spending that much on a pan I'd suggest getting one of their regular 3 qt sauciers -- you'll spend at least half as much.

If I only had one pan in my kitchen though, I think I'd still go back to the saute pan above. Its versatility is just unmatched.

Regarding your concerns that a wider pan won't heat as evenly, this is generally true for a cheaper pan. However, All-Clad pans use magic to bond a layer of aluminum (or copper) between a layer of magnetic stainless (exterior) and 18/10 stainless (interior). The end result is a very even heat which you can actually confirm with an infrared thermometer.