There are some "experts" that will probably give you a
better answer, but I think that the steel reeds are
much louder than brass?

--bn

Good question, and it got me thinking. (Always dangerous.) I pulled apart two I had at hand, a Hohner Blues Harp and a Lee Oscar. The Hohner plates and reeds look like steel, the Lee Oscar plates and reeds look brass. I'm not much of a harp player, but the brass reeds of the Oscar seem easier to "bend."

If I'm not mistaken, the early accordions had brass reeds, but they went to steel because the brass wouldn't stay in tune very well. May be a difference in the size??

I have a couple sets of brass reeds taken out of old Hohners that I don't know what to do with.

You are both right.
1. Brass reeds are not as loud as steel reeds.

2. Brass weighs three times as much as steel, so an according with brass would be much heavier.

3. Brass is a softer metal than steel and does not last as long.

4. Brass is much more expensive than steel.