The main difference between bladder and diaphragm hydraulic accumulators lies in their internal design and construction. Bladder accumulators use a flexible bladder to separate the hydraulic fluid from the gas, whereas diaphragm accumulators employ a flexible diaphragm to achieve the same separation. While both types operate on the same principle, bladder accumulators are more suitable for high-pressure applications, whereas diaphragm accumulators are better suited for low-to-medium pressure systems.