Originally Posted by xliioper

OP was asking whether or not it makes a difference to book exact same flights (presumably DL metal) on DL website or VS website as VS codeshare flights (not whether or not to book flights on VS metal or DL metal). They won't be eligible for Medallion C+ upgrades if booked on VS website as VS codeshare flights, but if passengers don't have status as indicated, that won't matter. However, if they are interested in possibly paying for upgrades to higher cabins, they also won't get any online upgrade offers if booked as VS codeshares. DL mileage earnings will be different if booked as VS codeshares vs DL coded flights and can be more or less depending on fare paid, fare class, and mileage flown. DL Basic Economy fares will not earn anything, while VS Light Fares (T class) still earn 25% of mileage flown.