- at worst you're getting a 7 year old monitor

- the new 5k XDR has 4x as many dimming zones so it would objectively look better than the old XDR

- not sure what the market for used 6k XDRs is like, but there's a good chance you'd be paying new 5k XDR monitor price for an old 6k XDR used monitor

The the smaller xdr has better brightness and thunderbolt 5, so it depends on what you are looking for.