There are pros and cons. Biggest pros are typically more exotic ports and a more mature passenger manifest. Cons are often a much older ship (Conquest, for example) a very homogeneous pax cruise style (MDR is totally jammed at 5:30) and a lot of scooters.
I love getting away for 14 nights. In my personal opinion, unless rare ports are part of the cruise, a B2B is a better idea. On our recent Journey we got to Dominica and Grenada so it was worth it.