I use metal tubes a lot for trout and salmon. Metal tubes will help you out if you want to avoid the probleme of have a bag form in your line when your tips are sinking but your plastic tube is floating higher in the water column. When this happens you have to pull all the slack out of the “bag” before your hook set hits the fish.
For the most part, aluminum tubes should serve the purpose most of the time, and they are not that difficult to cast. If you really need to get deep, you can go to the copper tubes but they are much harder to cast. Tube flies are a lot of fun, enjoy the journey