With attribute settings you can also define sorting keys – e.g. if you want to display weekday names (Monday, Tuesday, Wednesday etc.), then you need to sort it by weekday numbers (1, 2, 3 etc.).
Member properties are useful when you one-to-one relations between related dimensions attributes. E.g. ‘Vendor number’ and ‘Vendor name’ may be two separate dimension attributes, but by setting up one as a member property to the other, you can get better performing queries – and at the same prevent the client from displaying unnecessary subtotals.