What is the difference between baking bread in a loaf pan made of stoneware vs metal vs iron cast?
Sandwich or quick bread has different heat requirements than artisan breads.

Artisan breads require a blast of high heat and humidity right from the beginning. They are usually baked on flat, preheated stones that store a lot of heat.

With breads baked in loaf pans the bread is proofed in the pan which is obviously not preheated. The goal is not a blast of high heat but generally even heating.

Stoneware and cast iron will hold a lot of heat but that isn't very useful for this type of bread. The big difference that a stoneware loaf pan will make is in the bread's crust. Unglazed stoneware will let some moisture escape during baking. Stoneware loaf pans are often used for dishes other than bread such as meatloaf where the even heating and heat retention when serving is valuable. Bread baked in stoneware will be crustier in the area covered by the pan than bread baked in metal. This is a more compelling advantage with quickbreads. In my opinion sandwich bread doesn't need to be crusty.

Metal bread pans are cheaper, lighter, and less fragile. They won't even out any heat gradients in a sloppy oven. If you know your oven is unreliable consider getting a thermal mass (such as a pizza stone) to even out the temperature.

I haven't used a cast iron loaf pan but my first inclination would be to use it for southern-style cornbread. This type of cornbread is normally cooked in a cast iron skillet. The pan would be preheated with hot fat and the cornbread batter would be poured in. The stored heat in the pan would fry the bread before it rose and set. I don't know why a cast iron pan would be used for normal bread.