We've done it both ways. Our first cruise was entirely on points, but only because we had a bunch that we had to use. We purchased a resale and had a LOT of banked points that were going to expire if we didn't use them. The "point" cruise cost us 725 points for a Cat4 stateroom with 3 adults and 2 kids. The cash price for that cruise would have been around $7200, so I figured that we broke even.
Since then we've cruised 3 more times, each time paying cash rather than using points. The major advantage to booking with cash is the ability to latch on to the occasional "deal" that Disney throws out to the cruising public. The point cost of a cruise is determined at least a year in advance and, from what I've observed, is very inflexible in regards to
DCL special deals. If you book a
Disney cruise through a travel agent (like DreamsUnlimitedTravel.com for example), and Disney lowers the cost of the cruise, you can reap the benefit of a less expensive cruise.
If, on the other hand, you have tied up all your vacation money in DVC, your only recourse is to use points for the cruise (unless of course you want to rent out those points).
I made the mistake of telling my wife that it was "stupid" to pay cash for a cruise and that it was better to spend that money on points that could be used year after year. She holds me to that statement every time I bring up the subject of a cruise. Fortunately, the occasional bargain cruise does show up from time to time and I have been able to convince her that my thoughts on spending points versus cash on a cruise have changed.
Good luck with your decision. As you can see, this is not a black and white choice.