Change your preferences here.
Though Aqua Tail may possess superior Base Power to the most commonly seen physical Water-type attack, Waterfall, it is somewhat rarely seen due to its lesser accuracy, and the lack of a handy flinch rate. However, it may see some use on slower Water-types and on hit-and-run attackers, such as Choice Band Swampert, since neither would a miss prove pivotal, nor would a flinch be likely. However, where Aqua Tail sees most use is on the numerous Pokemon that do not learn Waterfall—for instance, a physical attacker such as Tyranitar could use it to hit the likes of Gliscor and Hippowdon. All in all, in almost any case where Waterfall is used, Aqua Tail is an option; the extra bit of damage can sometimes turn a 2HKO into an OHKO, though you must remember that a degree of consistency is lost. Often, you cannot afford to miss, but neither can you afford to fall short of a KO, so you must consider how much damage you are doing to common switch-ins before making this decision.
Waterfall is a less powerful move with perfect accuracy and a chance to flinch the opponent.