There are two designs of bed in a caravan. The first being an Island bed where the bed head is positioned at the front and you can usually walk down either side and faces north/south.
The second is the Yacht style where the bed goes across the front of the van from one side to the other or east/west.
Island beds are more popular, take up about two feet more of space, and the bed sometimes is shorter. The yacht style saves more room, the bed can be as long as the width of the van if you want it to, but the negative is one person is on the inside and has to climb over their partner to get out (or in for that matter).
We have a yacht style - I am tall so wanted the extra bed length and we wanted our van as short as possible. We like the design, and space saving aspect, plus it also allowed us to not only have a tunnel boot, but also a Weber Q slide out on one side and another slide out for a freezer on the offside. You can't have these two extra slide outs with an island bed.
As for resale - we haven't tried selling ours yet, but people can only buy what is available so we are not concerned about it.