LoyaltyLobby reader sent me an email to get my opinion what would be the best deal.
Here’s the summary:
Amtrak: 10% premium
United: Five United miles per USD loaded
Southwest: 12 Rapid Rewards Points per USD loaded
The Southwest one is most attractive IF you fly the airline and use the points for Wanna Get Away fares. 12 Rapid Rewards points is worth 20 cents.
The United offer is ok only if you redeem the miles for international business or first class travel.
My personal choice would be the 10% premium loaded for the card. Your $900 card purchase would turn to $990.
If you are staying a lot at Marriott hotels, you can use these gift card promotions to save money on your hotel spend by getting frequent flier miles in the process or premium loaded to your card. I have purchased these in the past, when Marriott has offered bonus Marriott Rewards points for the purchase that they tend to offer at the end of the year.