I would start with finding which airline has the most convenient schedule for your business travels. That will matter a lot. Then look at your personal travels and see if that is also convenient on the same airline(s). Also consider status and upgrades if you fly a lot.

Based on my mileage redemption experiences, especially for domestic flights, DL would be my very last choice. I am strong-armed into DL since I live in ATL. DL miles are still valuable for certain things but nearly worthless domestically (in my opinion) since the low level availability is pretty non-existent.

If you can afford the fees I would get the Chase Ink Bold/Sapphire and Platinum Amex. I use both myself and mainly have AMEX for sky club access, airline fee reimbursement, global entry, and priority pass. I use Chase Ink Bold for spending. I am currently hoarding Chase UR points for redemption later on for international biz/First class.

Also study BA's program. You can redeem BA Avios points for AA flights. It is distance based so short domestic flights can be 4,500 points each way in coach! You can transfer points from Chase UR and AMEX MR to BA.

Think outside the box!

Foo