Whirlpool recommends the use of tablet detergents over liquid detergents in its line of dishwasher appliances. The company do not, however, state that any particular brand of detergent should be used over another brand.
While powders and liquids can be used in Whirlpool dishwashers, the company recommends tablets for regular use. Whirlpool sites changes in government regulations determining the amount of phosphorus that are used in detergents as part of the reason for this decision, as well as convenience and their assessment of improved performance.
Beyond Whirlpool's own recommendations, research done by popular companies such as Sears has determined tablets to be more beneficial in use over powders and liquids as well. Their studies have concluded that tablets are better overall at removing heavy, grease-based stains. Tablets dissolve better in soft water and take out much of the guess-work in measuring, as they have been pre-measured for best results on average. Detergent tablets have also been found to prevent water spots from forming on glassware and to require less extra rinsing. Some drawbacks to tablet use may present themselves based on whether the water used in the dishwasher is hard or soft. As such, it is harder to make adjustments in detergent tablets, and experimentation with liquids and powders may benefit the situation overall.