Here are some examples to illustrate how to choose, but this is not a regulation. Each case can be considered individually.
If the rack is standing at the machine (laser / plasma cutting, guillotine, punching, bending, etc.) on which the sheet is placed by the operator manually, one by one, then we recommend
DRAWER rack. The operator pulls out the shelf with the needed item and takes one sheet to the machine table.
If the rack is used to feed the sheet to an automatic machine with automatic loading - consider
STACK rack. We put the whole shelf in the area of material fencing with an automatic loader, it takes the sheet and puts it on the table of the machine.
If you need to organize a compact storage of material (eg, now a warehouse outdoors or metal is stored in a pallet rack, which is less spacious) - use
STACK rack.