It is matter of choice. There are pro's and con's to both. We chose to rent 300 pts to pay for our cruise for next Feb. We saved 150 pts by renting and booking with cash through Dreams Unlimited.
It only took 1 hour on the Rent/Trade board and a few e-mails for me to rent my 300 pts
Some cons for using points................
When you use points you can't book it until 11 months out, and you may not get your cabin of choice.
There is a $75 fee booking with points. If you make any changes they(MS) charge you $75 again.
IMO I would never use points to cruise unless they were about to expire.