I'd never thought about it before, but I cannot imagine Sir W would marry anyone but a beauty.

It's also curious that Sir Walter, although he evidently loved his wife, thinks so little of Anne, who presumably took after her.

(Although, JA says: ...it was only in Anne that she [Lady Russell] could fancy the mother to revive again.
Anne is like her mother, but it doesn't specifically say she is physically like. The resemblance might have been in temperament, talents, etc.)