I've been using an Ozturk 10kg roaster for two years. The drum is cast iron. The results have been great. As an earlier poster said a lot has to do with the person doing the roasting but the roaster itself has done quite a good job for us. I don't have experience on steel drum roasters so I could be wrong but I know from cooking with cast iron pans and pots that I get a 'softer' more even heat than with steel (I hate my steel pans here in Irealand - horrible stuff. When I visit the States again I'm going to reclaim my well seasoned, naturally non-stick pans! -- but I digress).
I think Ambex used to have their roasters, or a large part of them made in Turkey and I don't find too many people dissing Ambex so that should give you an idea of the machinery.
I've said before that I consider my Ozturk to be like a good Ford or Chevy. It may not have all the bells and whistles that some have or the name cachet of, say, a Probat, but it gets us from point A to point B and we're very happy with the results. Maintenance is easy and we've had good response from the factory.
There is a guy in upstate NY, Duane, at Adirondak roasters. Give him a shout as he deals with Ozturk a lot. He is such a great guy that I called him from Ireland to get his opinion and even though he wasn't making a dime on the sale he still invited me to his place and gave me a day of roasting lessons for free. Someone asked about Texas and I know he has sold roasters into Texas so give him a ring. He'll treat you right.
Oh, finally, before I bought my Ozturk I did speak to the guy in Delaware and right off the bat got the feeling that he wasn't going to treat me right. If it is the same person mentioned earlier then I was right. But that was no reflection on the roaster, it was a reflection on the individual.
Best wishes on whichever roaster you purchase.