We have been cruising w RCCL since 2013 and always book onboard. I have always found that we get more OBC and deposit is less. We booked on our cruise earlier this month and got $500 OBC for booking a JS. I always research before we go and keep watch after we book and other than an occasional price drop, which they will honor, I have not found any reason not to book onboard, especially if you book those first 3 days and get extra discount.