Been on 4 Journey cruises, highly recommend them. Som much better than a B2B I will not even do the compare. In terms of the loyalty perks, there certainly are concessions in regards to the number of diamonds and plats, just part of the equation. I would never not do one because of this.
For us, the drawback (and it is minor) is the number of power scooters and smokers....
I can point you to some of my reviews if it would help.
Lastly, DO IT