I'd rather have had Walker for the past 2.5 seasons. No question.
Moving forward, Walker's age will become an issue, and looking back, we probably maximized the value we could get for Walker.
Walker is (per TransferMarkt) the 4th most valuable RB in the world and 2.5x the value of Aurier (who is tied for 23rd most valuable RB in the world.
Aurier is insanely undervalued IMO. His individual stats are ridiculous.
Defensively, he is 8th in the entire PL in tackles. 5th among all defenders.
Offensively, he is tied for 19th in the entire PL in assists. 3rd among all defenders.