There's a lot to like about Delta and they're my preferred carrier. But they've got a giant weak spot when it comes to long haul premium award ticket redemptions, where the miles required typically run the gauntlet between ridiculous and insulting. If that's your main redemption strategy, you're probably better off with American, though you have to be careful to avoid redemptions on partner BA flights that can come with big cash surcharges on long haul routes.