I'm glad to see there are some folks who find the per-day pricing useful. Personally, I think of "a cruise" as one unit.
Pre-retirement, I'd already know how many days I could take, so that wasn't something I needed to compare. Now, I wouldn't care if it were 7 days or 10 days. It' still "a cruise" that will cost me a total of X dollars. If it's in the budget, I'll go. If not, I'll wait.
Also glad the OBC's can be used for useful stuff. I remember one cruise where they didn't count toward booze, excursions or several other things we wanted. Only spa treatments and the like. I'm not a big spa user, so that didn't help me.