Why earn American Express Membership Rewards or Chase Ultimate Rewards points vs earning just Delta or United miles. Well a couple of reasons.
Flexible points can be used for more than just airlines and flights, like hotels and even gift cards and other airlines
You can earn flexible points at a faster rate than airline points and at more places
Flexible points are just that, they are flexible, and are used for nearly any time of travel expense. When I first got my American Express signup bonus I used all my points to get a flight to and from Seattle, rent a car and get a hotel room, all for “free”. I couldn’t do that with my Delta card signup bonus. With Chase you could book one way to, say New York, on United and home via Southwest. Or on American Express you could do there on Delta and home on JetBlue. Why do this? Maybe it is cheaper or the other airlines have better flight times, but either way flexibility is a great way to go.
With a standard airline card you can get 2 points per purchase on flights. With Chase you will get 3 points and with American Express you can get 5 points per purchase on flights. Not only that but everyday spend (spending you do everyday, like grocery store or starbucks) can earn a higher rate. With certain card pair-ups you can earn a non-category spend rate of 1.5 points per dollar spent or sometimes up to 4.5 points per dollar spent depending on your category spending (like in grocery store or in at a gas station). This helps you earn more points at a faster rate without spending more.
Don’t worry about transfer ratios nearly all Credit card transfer partners transfer at a 1:1 ratio so even though you are earning more miles on a flexible card you can transfer them as if you had the airline card. Plus plans can change and keeping your points in flexibility allows you to adjust your plans accordingly. So instead of flying to a location and getting a hotel, maybe you can drive and get an even better hotel.