Tank volume vs pressure

[Failure]

Im looking at a new tank. Now, what would be smarter to get:

a) a 68ci 3000psi tank

or

b) a 47ci 4500psi tank

Which would give more shots? I mean, wouldn't they both give around the same because the pressure of the 4500 vs the volume of a 68ci?

[headcase]

Yeah, assuming you always get a good 4500 psi fill, they would be pretty close.