Sorry for the diversion. Lets try this:

Since points or miles accrue per dollar, spend rate is irrelevant. Since you will likely use the same credit card either way, irrelevant as well.

So the question boils down to "which do you value more, 15 points or 6 miles?" (Assumes 10 point property and 50% bonus).

My rule of thumb is miles are a penny, points ate a half a penny.

So points. For me.