Gold: $95 annual fee, waived for the first year
Platinum: $195 fee
Reserve: $450 fee
A good card for a Delta frequent traveler, but I personally would not take the offer because of the annual fee. I think it makes more sense economically to get a Barclaycard Arrival Plus with its 2x miles on all purchases or a BoA travel rewards cards with 1.5 points for all purchases. The ease of redeeming that miles or points to any travel makes these travel rewards cards a perfect alternative to airline programs.
On the other side, Delta Sky Miles card and other airline cards offer you airline specific benefits like a priority boarding, free checked bags and free companion tickets. If you value these perks, then airline cards are your best choice.
Gold card is the cheapest with its $95 annual fee (waived for the first year), then goes the Platinum with $195 fee, and last comes the Reserve with a $450 annual fee. Platinum and Reserve offer you more bonus rewards for spending and MQM miles that go towards your elite status with Delta.