Reserved Instances provide a significant discount compared to On-Demand pricing in exchange for committing to a specific usage (1-year or 3-year term), making them ideal for workloads with predictable usage and the need for reserved capacity. Savings Plans also offer discounts but with more flexibility in usage. Spot Instances are unsuitable for essential, steady workloads due to the possibility of being outbid and terminated. On-Demand Instances are the most flexible but also the most expensive option for long-term, consistent workloads.