Bear in mind that I am not a "DIR Rep" or what-have-you, but this is my understanding.
Luxfer AL80s for stages, (and sometimes deco) and AL40s for deco.
Catalinas can be used, but the Catalina 80s are slightly heavier in the water, (only slightly), but it makes them ride terribly. I think the Luxfers are more butt-light than the Catalinas, and ride better when full, but as they get breathed down, the Catalinas start to ride better. (I did a back-to-back test with Catalina and Luxfer 80s, rigged up identical. The Luxfer rode better the whole time, but past 2500psi or so, the Catalina wasn't bad and got better the emptier it got.)
My personal opinion, the Catalinas make better backgas tanks because the butt of the tank is reportedly a bit heavier, (helps offset the weight of the tank shoulders and the manifold and regulators), so it balances and trims out better. (On me at least).
Problem for stages is that Catalinas are what's available new, (I like new), so unless you look used and avoid the TONS of older Luxfers made of the crispy 6351 alloy, (all Luxfers made after 1988 are OK, avoid earlier ones), you're stuck with Catalinas.
Don't know the difference between the AL40s, but enough people comment on them to make it sound like there is a difference. I work in a shop and can get Catalina AL40s for cost all day long, but I'm holding out for Luxfers if I can find some used at a good price. Trouble is, often times, people know what's up, so used Luxfer AL40s command "new" prices.
That's my brief experience.