The raised bed itself gets all the deliberation: which material, what height, cedar or metal or a kit, how it looks. Then, having spent their thought and money on the box, people fill it with whatever soil is cheapest and most convenient, and later wonder why their plants are stunted and sad. They have it backwards. The bed is just a container. The soil you put in it is the actual garden, and it is very nearly the whole decision.
Why the fill is everything
Plants do not grow in the wood or the metal; they grow in the soil, and everything that determines whether they thrive — nutrients, drainage, structure, the ability to hold the right amount of water and air around the roots — lives in the fill, not the frame. A beautiful, expensive bed filled with poor, compacted, or nutrient-starved soil grows poor plants; a plain, cheap bed filled with rich, well-structured soil grows a thriving garden. The entire point of a raised bed is to give you control over the growing medium, and squandering that by filling it with bad soil wastes the whole exercise.
Why people get it wrong
Because the bed is the visible, exciting, purchasable object — the thing you build and photograph — while soil is unglamorous, heavy, and feels like a commodity you just need to fill the volume with. So the deliberation and money flow to the structure, and the soil is an afterthought chosen on price. But the structure is scenery and the soil is substance, and a garden lives or dies on the substance.
The takeaway
Treat the soil as the real decision in raised-bed gardening, because it is. Choose a simple, functional bed, and pour your thought and budget into filling it with rich, loose, well-draining soil that will actually grow things. The bed is a container; the soil is the garden, and no amount of lovely woodwork compensates for poor fill. Get the soil right, and even the plainest bed produces a thriving garden — which was the whole reason to build one.