Answer
Inward swing doors are usually more popular . This is because they are more effective for door seal than outward swing doors.
Inward swing doors do not impede the user from entering or exiting the bath or easily closing the door once inside the bath. Inward swing doors are not restricted from opening because of other fixtures in the bathing area such as vanities or water closets. They also do not require a significant latching system to keep the door closed while the bath is filled.
Inward swing door seals are enhanced as the bath fills and the seal becomes more efficient. Inward swing doors cannot be accidentally opened during bathing, which could result in flooding of your bathroom. Inward swing doors do not require an exterior drain because of potential door leakage. They do not require devices for adjusting door tension to prevent leaking. With an inward swinging door there is no residual water runoff from the door that falls onto the floor outside the bath that could be a safety concern when exiting the bath and stepping onto this area.
Inward swing door bath design can accommodate a larger volume of water. This is an advantage not a disadvantage. Most outward door swing baths are extremely small and uncomfortable and are designed smaller because the amount of force that would be required to keep an outward swing door closed that had a larger water volume would be extreme.