Battlefield 3 may be winning the war against Call of Duty: Modern Warfare 3 in one area: pre-order sales.
According to a GameStop source, Battlefield 3 leads preorders for the retailer over Modern Warfare 3, but, dubiously, the source also claims GameStop is pushing Battlefield 3 over Modern Warfare 3. It's doubtful that such preference is desired by a retailer.
Regardless, pre-order sales do not equate into more sales. Most sales are in-store pickups. What one might infer from the rumor is that Battlefield has a stronger fanbase who will make the game review-proof, while Modern Warfare attracts more casual gamers through brand recognition and trust.