The royal suites do not have jacuzzis on the balconies. Only the penthouse suite has that on the Mercury. However, the extra separate living area in the RS makes it my choice over the Sky Suite. Also, a portion of your balcony is viewable to others in the Sky Suite. You have more privacy in the RS.
You can get the butler service also in Cat 01 I believe. However, since I can do without the butler service, I based my decision on the space and configuration of the room. It really is a personal choice!