Without further info and as a general answer, choose the 28 incher. No doubt.

The 32" is heavier to start with. Tare weight is higher. Thus net load weight goes down because you have a 50lbs limit.

Besides, on some strict airlines you might run into dimension trouble at check-in.

Also, you usually want stuff to fit snugly into your suitcase. When the suitcase is too big for the contents, things will slide around inside. Normally not desirable.

Only exception, you need to transport things that are rather lightweight but simply don't fit into the smaller 28" frame, e.g. art work or vases.

For ordinary use even a 25 or 26" model will do, when filled with the usual assortment of clothes/shoes and a bit of paperwork or books.

Till