I have a 4040pro. It's been quite decent in wood, but I don't know about soft metals. The round tubes are just that, tubes. This makes it easier to deflect towards the center of the work area. I had hoped they were solid rods. I think that would have been less prone to deflections.
That being said, I am working towards doing a couple small brass projects on mine though. I think it would be capable with low feeds and small cuts. I am not sure how confidant I am abouts it's detail though.