There's a good municipal campsite right in the middle of Macon - really convenient for the autoroute, and you'll have a much quieter night there. This section of autoroute is really busy, with traffic flying past all night - and trucks pulling into and out of the service area. Personally, in that area, I'd choose the campsite (and we do stay on Aires in other parts of France - so it's not because of any other issues).