Be aware that the DL Amex Reserve card only offers triple miles on DL purchases, and one mile on other purchases. SkyClub access is included.
The DL Amex Platinum card earns the same, but also double miles on restaurants, double on supermarkets, and triple on hotels. However, Skyclub access is not included, but can be purchased for $50 per visit. If you don’t visit a club enough to offset the cost of a Skyclub membership or Reserve annual fee, the DL Amex Platinum is a better value IMO due to the higher mileage earning potential.
Note these are the “DL Amex” cards, not the traditional Amex cards which each have different policies.