Since your travel patterns are so fixed, it's hard to get more value than a cashback credit card. The B6 and US credit cards don't offer category multipliers except on purchases from the airlines. So, since you're earning 1 point or mile per dollar, it's going to be very difficult to earn more than 2% of cash value.

While I appreciate that my analysis may (or may not) be helpful - you really will want to validate all the numbers because everything hinges on the low-ish value your situation gives to airline points/miles.

There is one more popular 2% card: Fidelity Investment Rewards Amex

No annual fee, pays out 2% on everything, but it's an Amex so acceptance can be tough.

Also consider signup bonuses: The US card has a 40k miles signup bonus right now. If you can get 2 cents/mile from those miles, the signup itself is worth $800 to you and that's enough of a reason to get the card.

Also, if you need a trip outside your usual travel plans, then everything could change, obviously.