That really depends on what you're storing, how much you're storing, and how often you want to access it. Cisco-Eagle can assist you specifying the kind of storage rack that will give you the best service for your application. But in general, here are the types of rack and when you should consider utilizing each.
Selective pallet rack is easily the most versatile choice. It provides 100% selectivity to every pallet position. You can have as many SKU's as you have pallet positions. You can easily change the storage mix. You can always access every pallet. However, selective rack requires numerous aisles and has lower storage density than some other alternatives. It's the most common pallet storage racking type in the world. It's best for faster moving product, and the best access, selective racks are the system of choice. (Pictured below: Selective racks require aisle space but deliver maximum access to stored pallets).
These systems are designed to store pallets two, three, or more deep. These kinds of rack systems offer greater storage density than selective racks, but less selectivity. They are "last-in, first-out" systems with reduced selectivity, and great product density. For items that will have longer life in storage, and don't require immediate access, these systems are an excellent solution. (Pictured below: these racks offer greater storage density at the cost of accessibility).
In a pushback rack system, pallets are placed by forklift on nested carts riding on inclined rails. Each pallet is then pushed back by subsequent pallet loading, exposing the next cart. This is by nature a last-in, first-out storage media. Unlike drive-in racks, you can place a different SKU on every level. The trade-off is twofold: First, pushback systems need angled pitch so that pallets push to the front once one is removed, meaning that vertical space is consumed since each level must have an angle. These racks don't allow as many pallets in depth as drive-in systems, so they aren't as high density. But for those areas where more selectivity is needed than a drive-in system allows, and where more storage density is needed than a selective rack system allows, pushback is ideal.
Unsurpassed storage density is the key strength of pallet flow rack systems. They are limited only by the size of your facility. Flow storage systems offer automatic "first-in, first-out" product rotation, an advantage with perishable and time-sensitive products. (Pictured below: Flow storage is the ultimate in high density storage, with the product access limited to the front of the system).
Other factors, such as rack type (structural, tubular, boltless, open back, etc.) may play into your final decision. You can also increase storage density and retain some flexibility with other methods, including Flow Rail horizontal pallet flow rail systems that combine some of the "best of all worlds" in high density applications. We can help you design the ideal pallet storage system for your application.