All three hold soil. They don't hold it for the same length of time, and they don't fail the same way.
Poured concrete
The most structurally capable of the three, well suited to taller walls and heavier loads above. It costs more up front and needs footings and reinforcement sized to the job.
Block systems
Modular block is common, looks tidy, and works well at moderate heights when the base and drainage are done properly. Height limits and surcharge above the wall are the constraints to respect.
Timber
Cheapest to install and the shortest-lived. In our wet winters and dry summers, timber walls have a finite lifespan — we'd rather you know that before you build one.
The factor that outranks material
Drainage. Walls fail because water builds pressure behind them, not because the material was wrong. Every wall we build has a drainage plan behind it.
The short version
Choose material for height and look — then spend the attention on drainage, which decides survival.
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