Honestly, the biggest thing people miss is the shed floor itself... a custom build lets you anchor right into the floor joists for serious strength. Those pre-made racks often just sit on the floorboards, which can sag over time with heavy stuff like tools or paint cans. Building it yourself means you can make the bottom shelf extra strong for the really heavy items. It's a bit more work up front, but it saves a headache later when your storage doesn't buckle under the weight.