I've seen it done both ways on a couple of things, an Enco bp clone, and a Startrite automatic bandsaw. I believe they brass didn't last as long, and was very noisy when freshly done, and even worse when it started to wear, and on the mill, the plastic was pretty quiet all the way until it wore enough to need bushing again. This was in a jobshop, where the use was daily on both. I think the right plastic would be my choice. I hate noise. I don't think it lasts as long, but it's definitely quieter.