The choice between a shower seat or a shower bench for a bathtub depends on individual preferences and needs. Both shower seats and shower benches can provide a safe and comfortable seating option in the bathtub. Here are some factors to consider when choosing between a shower seat and a shower bench for a bathtub:

1. Space: If you have a small bathtub, a shower seat might be a better option as it takes up less space. A shower bench is generally wider and longer, so it might not fit well in a smaller bathtub.
2. Mobility: If you have limited mobility or difficulty standing for an extended period, a shower bench might be a better option as it provides more support and stability than a shower seat.
3. Comfort: If you prefer to sit more comfortably and have more space in the bathtub, a shower bench might be a better option as it provides more seating area and often comes with a backrest and armrests.
4. Durability: Shower benches are generally more durable than shower seats due to their larger size and stronger construction.

In summary, both shower seats and shower benches can be a good option for a bathtub, but the choice depends on individual needs and preferences. A shower seat may be more suitable for smaller tubs or for people who do not require a lot of support, while a shower bench may be more comfortable for people who prefer to sit and have more space or require more stability and support.