One integrated management system, or three separate ones?

ISO 9001, ISO 14001 and ISO 45001 share the same high level structure, so integration is possible and is usually recommended. It gives one document set, one audit programme and one management review. It also means a weakness in the shared elements is a weakness in all three certificates at once, and it puts quality, environment and safety in front of the same management review agenda, where safety tends to lose to delivery. If you integrated, what did you actually merge and what did you deliberately keep apart?