When choosing a bench you should take into consideration the one that encourages good posture but that is still comfortable and easy to use. A bench that does not encourage good posture can end up causing back pain, wrist and neck pain, and can make playing wholly unenjoyable.
piano bench
Piano stool and Piano bench differences

Conventionally, piano benches are longer, a little heavier, and bigger than stools, and ultimately are more of a styling choice, so for the purposes of today, we will be using the two terms interchangeably

The things to consider when buying a piano stool:

Comfort and Stability
If you’re not comfortable at your stool or bench you won’t have a great time playing your instruments, that’s why many companies such as Geekstands.com have invested countless of time to make some comfortable benches and stool. Stability should also be taken into account so that you are comfortable when playing. Checking nuts and bolts from time to time is needed to maintain good stability.

Style and décor
A piano bench that will match the style and décor of and the room it kept in

Cushion Thickness
Piano benches without cushions may look cool they aren’t as cool if you sit on them. Imagine you’re practicing an hour or a half what does it feel like. If you’re buying piano benches from a store make sure to sit on them to test them out if you’re browsing online read the product descriptions