Walk-In Tub vs. Walk-In Shower
Both reduce the need to step over a traditional bathtub wall, but they provide very different bathing experiences.
By Everyday Home Advice Editorial Team

Both reduce the need to step over a traditional bathtub wall, but they provide very different bathing experiences.
Walk-in tub
Potential advantages: seated bathing, soaking, lower entry than a traditional tub, and an integrated seat. Considerations: the user normally remains inside while filling and draining, hot-water demand, door operation, the entry threshold, and transfer ability.
Walk-in shower
Potential advantages: faster entry and exit, more open space, flexible grab-bar and seating options, and potential compatibility with mobility devices depending on the design. Considerations: proper waterproofing, drainage, floor slope, slip resistance, shower controls, and the door or curtain configuration.
Which is better?
Neither is universally better. Ask whether the user wants to soak, can stand safely, prefers seated bathing, needs wheelchair access, and how much space the existing bathroom allows. Design around the person who will actually use it.