I have to agree, pick POINTS.

I just took a couple extra days in London after a business trip, and by having the points, I got to stay in a wonderful hotel that would have otherwise cost me $400 a night.

The general rule I go by (rightly or wrongly) is you take the currency of the company you're directly dealing with -- because you end up getting more for it. If you go with miles in this instance, Marriott has to buy those miles, so you're not necessarily going to get as much bang for your buck as you would have by taking points that Marriott themselves make good on, presumably at a lower cost. Of course, if you're saving for a particular goal (like mileage to take the family or friends somewhere), then take the miles.

[Rereading that last paragraph, I'm not sure if that was clear, holler if it wasn't!]