Well, I finally got around to trying this out, and the spawn rates are very differant. I only had about 10 mins left so I only put in 5 obsidian. At the end I got 11 iron ingots. I tried again because I had enough time(with 5 iron ingots again) and got 42 iron ingots. I think the explanation to this is that it was my second time around and some golems from the first time were still coming in.