I'd never sailed Royal Caribbean, spending most of my cruises on Celebrity. There is definitely a quality difference. The Jewel is older, heading in for renovations next year. You can tell it needs it. Most finishes are a bit shabby and it seems like things can never quite get clean. The outside balconies are kind of a mess.
Common areas are worn and the bars don't have much in terms of amenities. The first morning the buffet area was chaos-complete total 100% chaos. No plates, no food, staff clearly had no idea what to do. We heard rumors of everything from no dishwashers working to an inspection taking place to simply 'we don't know.' I've never experienced anything like it. We saw a same server that same night at dinner and she begged us to come back to try it again-clearly understanding how bad it was. Food overall was very ordinary, without much variety.
I'm used to staff members going out of their way to be helpful and that certainly wasn't the case in most instances. We called down for small items 2 or 3 times before anyone would respond, and then the attitude was 'huh-I guess we haven't gotten to it yet.' There were a few notable exceptions but overall, the staff was not outgoing and helpful.