hhdl

For spend-based earning programs, it's generally better to use partner earning (e.g. fly DL-coded and credit to AFKL) on discounted tickets and regular earning (e.g. AFKL-coded and -credited) for full-price.

DL RDU-DTW-BOS in F (I booking class $227 base fare) earns (no-status):

1700ish FB miles (and 12% of the way to ST Elite) vs.
1135 DL miles (and 13% of the way to ST Elite with accelerators)


​​​​​​Conversely, crediting CDG-AMS to DL is 1000 DL miles in business class.

Edit to add: this is most especially so when paying for premium cabins: if always flying Y, there's a case that partner-crediting is giving up too much.