If you are wondering which Amex card to get to maximize your points usage, this guide is for you. For regular American Express cards like the Green, Gold, or Platinum Amex, your point conversions looks like this:
100 points per $1 when booking airfare through Amex Travel
133 points per $1 when booking hotel through Amex Travel
166 points per $1 when using points to cover purchases already made
200 points per $1 when trading in points for an Amex Gift Card.
^ Lets be real, most of those are pretty awful really.
However, with American Express Blue Sky, your point conversion is MUCH better. You can apply your points towards travel charges that show up on your account for things like airfare, hotel, and rental cars. The point conversion looks like this:
7500 points per $100 credit, or 75 points per $1.
The way to get the most out of these points it to use them to cover parts of a travel related purchase. If my airfare was $375, then I would apply 22,500 points to cover $300 of that charge. I would not apply 30,000 points to cover the whole airfare, because when it's not in even $100 increments, you lose the remainder. In that case, 22,500 would cover $300, but the final 7500 points would cover $75, at a conversion ratio of 100 points per $1 (not as good). Therefore, always apply your blue sky points in even $100 increments to get the most of your point's conversion.
Bottom line, if you want to play the Amex point game to win, use a platinum card to get the preferred airline credits, lounge access, TSA/pre or Global Entry, platinum concierge, or any of the other nice benefits that come with the card. Then try and use the Amex Blue sky for the bulk of your purchases as to accumulate points on the account with the better point's conversion ratio.