Ok, I'll bite. The choice: aluminum trailer or a steel trailer plus a good bull. Same dollars.

I have a 10 year old corn pro steel, don't use it very much but definitely not worth zero. I think I could sell it for what i paid for it. I clean it out after every use.

I can see going aluminum if you use it a lot. I can about buy two corn pros for the price of a similar good quality aluminum trailer.

An important point in longevity of steel trailers is the fact that some steel trailers have a much better original paint job than others. A well made steel trailer with a very good OEM paint job (frame painted before floor put in for one) is not going to be worthless in 10 years in most small-herd service.