Insulation

[Adger Smith]

I haver a 32 X 12 Portable metal building I want to finish out the inside.
Will be for storage and messing with my Brass and Bullets.
Studs are 24" centers and are full studs.
Would you use foil backed styrofoam or have it spray foamed as a barrier between the metal and inside panels?
Should there be a moisture barrier installed with either insulation?
Is one way cheaper than the other?
I do realize the foam is way less labor intensive for me...
BTY this is in SW Arkansas near the Ar/Tex border... Heat is more of an issue here than cold...