Chicago O'Hare has only two Priority Pass lounges and neither is exceptional — both are in Terminal 5 (international). The Air France KLM Lounge has better natural light and a decent buffet. The Swissport Lounge is small with no windows but has evening hot food. Only relevant if flying internationally from Terminal 5.
Our take
If you have Priority Pass at ORD, go to the Air France KLM Lounge over Swissport — it has windows, more natural light and a better buffet. But neither lounge is worth a terminal change.
