In general, the consensus is that points are better than miles.

Assume you spend $25,000 with Marriott. If you take points, you will end with 250,000 points with no bonuses at all (not a likely scenario, but a conservative one for this comparison). If you take miles, you will get 75,000 miles in the airline of your choice at a rate of 3 miles per dollar (note that some Marriott brands only pay 1 mile per dollar).

For 250,000 MR points, you can cash an award that will yield 7 nights at any Marriott worldwide plus 100,000 miles on the airline of your choice. Even with this conservative scenario, points are better.

Typically, you can acheive 250,000 points quicker through various bonuses. If you are platinum and use the Marriott Visa for your stays, you will accrue 16 points per dollar spent. Using these permanent bonuses you reach the 250,000 point level by spending $15,625. Other normal bonuses will get you to 250,000 points even quicker.