Not sure if this is news, but I just found out that you can convert Reward points to miles.

10,000 points = 2,000 miles 5 points/mile
20,000 points = 5,000 miles 4 points/mile
30,000 points = 10,000 miles 3 points/mile

I ran some numbers thru Excel. If you except to earn 3,000 or more points during the stay, take the points, else take the miles.