Morning everyone
We are doing the B2B because we want to be on the ship for a full week. I have done a 4 night cruise before and it's just not enough time. I am looking at the day in between as a port type day, get off the ship a little and then spend time at the pool. Most people don't do the pools the 1st day so it won't be too crowded.
We're doing B2B because the Dream is only doing 3/4 days cruises and separately they are too short. I prefer at least a 7 day cruise (love the 14 day ones). Doing a 3/4 day B2B does make it a 7 day cruise that also counts as 2 cruises towards the Castaway Club. The October cruises will be our 9th and 10th cruise making us Platinum for the Fantasy MV so, maybe we will be able to book Palo or Remy on that cruise.
As DVC members booking with points, there really isn't a difference in the points for a 3/4 day B2B vs a 7day when looking at the per day breakout. It is only like 1pt difference.
Besides, when flying from CA it makes more sense for a B2B as I don't have to pay for two extra plane tickets or travel days. If I lived within a day's driving time, I would probably do more shorter cruises but having to fly, I want to increase the ratio of sea days to fly days.

Looking at the point values for the Fantasy, they do not seem any more expensive than the Dream except that the Fantasy is only doing 7 day cruises. I would love to do a B2B on the Fantasy which would be a 14 day Carribean cruise with 1/2 western and 1/2 eastern. But the Fantasy is only doing Western Carribean cruises for the first three cruises and we are already booked on the MV. Oh well, maybe the following year if money holds.