There are no special benefits for booking with points, it's just a matter of whether it's convenient for you to use your points or not. The only items your points cover are the cost of the cruise, taxes and fees. Ground transportation, Palo fees, excursions, etc. are all extra and not discounted. The date you can make reservations doesn't get pushed up either.
We choose to cruise on points because we have enough extra points. I value the points at what it costs me ~$7.50 per point (maintenance+ initial cost/# of years no financing) because I have no intention of renting my points out. My upcoming cruise is 510 points, so ~$3825. If I were to pay cash for that cruise, it'd cost me $4143. By using my points I'm 'saving' about $300. If I was in a pinch for points, I'd save them but we since we still have some left over to bank some into next year, for us cruising on points was a no brainer.