stephencilento
Generally divers move to steel for
- increased gas supply (bigger tank)
- buoyancy characteristics (may weigh less & finish more negative)
- perceived increase in durability/value
The best thing to do is educate yourself and then barrow/rental a few options. Faber offers 13 sizes of steel scuba cylinders not counting the ones for rebreathers.
Until you know why you need/want a steel cylinder the AL80 is fine.
WTF!?
This is one of the big problems with forums and their 'experts'. You just butchered a basic part of [scuba] science and people are thanking you it!?
Only the change in weight/mass would be exactly the same.
Buoyancy is more about relative density than it is about weight.
To say that the tank material is irrelevant is completely wrong because the tank material can be a significant factor of the object's density. Since density is determined by weight (mass) AND displacement (size) a cylinders buoyancy swing may be primarily, but completely, determined by its working volume.
LP120 goes from -4.87 to 4.07 = 8.94 swing (19L displacement)
HP120 goes from -8.82 to 0.65 = 9.47 swing (12.9L displacement)
The difference above is primarily explained by the HP cylinder's smaller displacement.
Buoyancy - Wikipedia, the free encyclopedia