I can only speak to my personal experiences when tungsten first came to market. Being a guide at the time and hating the cost increase, I tried brass on one client and tungsten on the other. There was literally no comparison between how many more fish the tungsten beads turned versus brass beads. Since then I have seen it fishing with buddies who were fishing brass while I scorched them with tungsten. Everything equal...depth, drift etc etc and the tungsten simply worked better for the style of nymphing we do consistently.
When it comes to midges, tungsten is a must IMO unless fishing in the film where glass seems to work as well as anything, but with deep midging it makes a huge difference.