What are they used for??
MFF or Scuba??
In the case of scuba, I personally think steel is better for one large reason,, weight. If you use a tank that is 30% lighter,, you will need to add lead ballast to offset the buoyancy.
If it's MFF, just the opposite, almost, you get to jump more MRE's..
last I looked in 2008, there were other issues:
1)Spun-glass tanks have shorter life spans
2)none of the scuba hydro shops in my area would touch them for hydro or annual visual inspections
3)They are very expensive.
4)dive shops won't fill them, non-standard valve
5)they came with valves for air-soft hoses or fire department 1st stages reg, not scuba.
Has the industry changed direction??