I am almost positive the two are mutually exclusive.

I originally signed up for Stay 3 Get 1.
Then, I determined that I'm actually better off doing the DL promo.
I switched my earning preference to DL and signed up.

Now I'm showing both promos, but I hope the system automatically figures out that I'm set to earn DL miles and therefore credit the DL promo.

Has anyone actually seen this work properly? I guess the real test can't fully prove it out until we're into June... I just don't want something in the system to default me back to Points in the middle of my Delta stays.

(Basically, I'm valuing 15,000 DL miles greater than 1 Cat 4 night - something I think most FT'ers would do even when they don't particularly like Delta. I'm rarely in a Cat 4 hotel where I couldn't have booked it or something similar for less than $150 direct or less than $100 Priceline.)