Difference between D-1 and D2?

[JeannetteC]

D-1 balcony cabins are more expensive than D-2 balcony cabins. I thought it was supposed to be a location issue but I've seen many D-2s in as good or better locations. I recently booked a D-1 and later found a D-2 which had just become available in a better location. My agent said she thought it was confusing but that one reason the D-1's were more expensive is because they have sleeper sofas.

 

I switched to the D-2 and received a small credit.

 

Is that the only difference? Does any one have any clarification on this?