You probably want to book the AF flight numbers because...
1. Air France charges for seat selection on both regular economy fares and basic economy fares. I believe you will receive free standard seat selection as a Silver Medallion.
2. Air France basic economy fares will earn RDMs, MQMs, and MQDs.
3. Delta.com will price a completely AF-marketed transatlantic itinerary, which may let you use your Delta eCredits. You usually have to use something like ITA Matrix PowerTools for this.